borylation

As first described by Hartwig, alkanes can be selectively borylated with high selectivity for the primary C–H bond using Cp*Rh(η⁴-C₆Me₆) as the catalyst.{{cite journal | last1 = Chen | first1 = H. | last2 = Schlecht | first2 = S. | last3 = Semple | first3 = T. C. | last4 = Hartwig | first4 = J. F. | year = 2000| title = Thermal, Catalytic, Regiospecific Functionalization of Alkanes| journal = Science | volume = 287 | issue = 5460| pages = 1995–1997 | doi = 10.1126/science.287.5460.1995 | pmid = 10720320 | bibcode = 2000Sci...287.1995C}} Notably, selectivity for the primary C–H bond is exclusive even in the presence of heteroatoms in the carbon-hydrogen chain. The rhodium-catalyzed borylation of methyl C–H bonds occurs selectively without a dependence on the position of the heteroatom. Borylation occurs selectively at the least sterically hindered and least electron rich primary C–H bond in a range of acetals, ethers, amines, and alkyl fluorides.{{cite journal | last1 = Lawrence | first1 = J. D. | last2 = Takahashi | first2 = M. | last3 = Bae | first3 = C. | last4 = Hartwig | first4 = J. F. | year = 2004 | title = Regiospecific Functionalization of Methyl C−H Bonds of Alkyl Groups in Reagents with Heteroatom Functionality| journal = J. Am. Chem. Soc. | volume = 126 | issue = 47| pages = 15334–15335 | doi = 10.1021/ja044933x | pmid = 15563132 }} Additionally, no reaction is shown to occur in the absence of primary C–H bonds, for example when cyclohexane is the substrate.

File:Aliphatic C-H borylation-3.jpg

Selective functionalization of a primary alkane bond is due to the formation of a kinetically and thermodynamically favorable primary alkyl-metal complex over formation of a secondary alkyl-metal complex.{{cite journal | last1 = Hartwig | first1 = J. F. | year = 2011 | title = Regioselectivity of the borylation of alkanes and arenes | journal = Chem. Soc. Rev. | volume = 40 | issue = 4| pages = 1992–2002 | doi = 10.1039/C0CS00156B | pmid = 21336364 }}

File:Primary versus secondary metal-alkyl complex.jpg

The greater stability of primary versus secondary alkyl complexes can be attributed to several factors. First, the primary alkyl complex is favored sterically over the secondary alkyl complex. Second, partial negative charges are often present on the α-carbon of a metal-alkyl complex and a primary alkyl ligand supports a partial negative charge better than a secondary alkyl ligand.

The origin of selectivity for aliphatic C–H borylation using rhodium catalysts was probed using a type of mechanistic study called hydrogen–deuterium exchange. H/D exchanged showed that regioselectivity of the overall process shown below results from selective cleavage of primary over secondary C–H bonds and selective functionalization of the primary metal-alkyl intermediate over the secondary metal-alkyl intermediate.{{cite journal | last1 = Wei | first1 = C. S. | last2 = Jimenez-Hoyos | first2 = C. A. | last3 = Videa | first3 = M.F. | last4 = Hartwig | first4 = J. F. | last5 = Hall | first5 = M. B. | year = 2010 | title = Origins of the Selectivity for Borylation of Primary over Secondary C−H Bonds Catalyzed by Cp*-Rhodium Complexes| doi = 10.1021/ja909453g | journal = J. Am. Chem. Soc. | volume = 132 | issue = 9| pages = 3078–91 | pmid = 20121104}}

File:Mechanistic pathways for aliphatic C-H borylation-1.jpg

The synthetic utility of aliphatic C–H borylation has been applied to the modification of polymers through borylation followed by oxidation to form hydroxyl-functionalized polymers.{{cite journal | last1 = Kondo | first1 = Y. | last2 = Garcia-Cuadrado | first2 = D. | last3 = Hartwig | first3 = J. F. | last4 = Boaen | first4 = N. K. | last5 = Wagner | first5 = N. L. | last6 = Hillmyer | first6 = M. A. | year = 2002 | title = Rhodium-Catalyzed, Regiospecific Functionalization of Polyolefins in the Melt| journal = J. Am. Chem. Soc. | volume = 124 | issue = 7| pages = 1164–5 | doi = 10.1021/ja016763j | pmid = 11841273 }}

File:C-H borylation of polyolefins-3.jpg

The first example of a catalytic C–H borylation of an unactivated hydrocarbon (benzene) was reported by Smith and Iverson using {{chem name|Ir(Cp*)(H)(Bpin)}} as the catalyst. The efficiency of this system, however, was low, providing only 3 turnovers after 120 h at 150 °C.{{Cite journal|last1 = Iverson|first1 = Carl N.|last2 = Smith|first2 = Milton R.|date = 1999-08-06|title = Stoichiometric and Catalytic B−C Bond Formation from Unactivated Hydrocarbons and Boranes|journal = Journal of the American Chemical Society|language = en|volume = 121|issue = 33|pages = 7696–7697|doi = 10.1021/ja991258w}} Numerous subsequent developments by Hartwig and coworkers led to efficient, practical conditions for arene borylation. Aromatic C–H borylation was developed by John F. Hartwig and Ishiyama using the diboron reagent {{chem name|Bis(pinacolato)diboron}} catalyzed by 4,4’-di-tert-butylbipyridine (dtbpy) and {{chem name|[Ir(COD)(OMe)]₂}}.{{cite journal | last1 = Hartwig | first1 = J.F. | year = 2012 | title = Borylation and silylation of C-H bonds: a platform for diverse C-H bond functionalizations| journal = Accounts of Chemical Research | volume = 45 | issue = 6| pages = 864–873 | doi = 10.1021/ar200206a | pmid = 22075137}} With this catalyst system the borylation of aromatic C–H bonds occurs with regioselectivity that is controlled by steric effects of the starting arene. The selectivity for functionalization of aromatic C–H bonds is governed by the general rule that the reaction does not occur ortho to a substituent when a C–H bond lacking an ortho substituent is available. When only one functional group is present borylation occurs in the meta and para position in statistical ratios of 2:1 (meta:para). The ortho isomer is not detected due to the steric effects of the substituent.{{cite journal | last1 = Ishiyama | first1 = T. | last2 = Takagi | first2 = J. | last3 = Ishida | first3 = K. | last4 = Miyaura | first4 = N. | last5 = Anastasi | first5 = N. | last6 = Hartwig | first6 = J.F. | year = 2002 | title = Mild Iridium-Catalyzed Borylation of Arenes. High Turnover Numbers, Room Temperature Reactions, and Isolation of a Potential Intermediate| journal = J. Am. Chem. Soc. | volume = 124 | issue = 3| pages = 390–391 | doi = 10.1021/ja0173019 | pmid = 11792205 }}

File:Meta-para borylation.jpg

Addition of Bpin occurs in only one position for symmetrically substituted 1,2- and 1,4-substituted arenes. Symmetrical or unsymmetrical 1,3-substituted arenes are also selectively borylated because only one C–H bond is sterically accessible.

File:Steric-directing Iridium Catalyzed C-H Borylation.jpg

This is in contrast to Electrophilic aromatic substitution where regioselectivity is governed by electronic effects.Liskey, C. Iridium-Catalyzed Borylation of Aromatic and Aliphatic C–H bonds: Methodology and Mechanism. Dissertation, University of Illinois. Urbanan-Champaign. 2013.

File:Complementary selectivity with C-H functionalization reactions.jpg

The synthetic importance of aromatic C–H borylation is shown below, where a 1,3-disubstituted aromatic compound can be directly converted to a 1,3,5-organoborane compound and subsequently functionalized.

File:Meta-functionalization of arenes through C-H borylation-2.svg

Aromatic C–H functionalization was successfully incorporated in the total synthesis of Complanadine A, a Lycopodium alkaloid that enhances mRNA expression for nerve growth factor (NGF) and the production of NGF in human glial cells. Natural products that promote the growth of new neural networks are of interest in the treatment of diseases such as Alzheimer's disease.{{cite journal | last1 = Fischer | first1 = D.F | last2 = Sarpong | first2 = R. | year = 2010 | title = Total Synthesis of (+)-Complanadine A Using an Iridium-Catalyzed Pyridine C−H Functionalization| journal = J. Am. Chem. Soc. | volume = 132 | issue = 17| pages = 5926–5927 | doi = 10.1021/ja101893b | pmc = 2867450 | pmid = 20387895}} Complanadine A was successfully synthesized using a combination of direct aromatic C–H borylation developed by Hartwig and Ishyiama, followed by Suzuki–Miyaura cross coupling, then cleavage of the Boc protecting group.

File:Synthesis of complanadine A.jpg

Heteroarenes can also undergo borylation under iridium-catalyzed conditions, however, site-selectivity in this case is controlled by electronic effects, where furans, pyrroles, and thiophenes undergo reaction at the C–H bond alpha to the heteroatom. In this case selectivity is suggested to occur through the C–H bond alpha to the heteroatom because it is the most acidic C–H bond and therefore the most reactive.

File:C-H borylation of heteraromatics.jpg

Using the same catalyst system directing groups can be employed to achieve regioselectivity without substituents as steric mediators. For example, Boebel and Hartwig reported a method to conduct ortho-borylation where a dimethyl-hydrosilyl directing group on the arene undergoes iridium catalyzed borylation at the C–H bond ortho to the silane directing group.{{cite journal | last1 = Boebel | first1 = T. A. | last2 = Hartwig | first2 = J. F. | year = 2008| title = Silyl-Directed, Iridium-Catalyzedortho-Borylation of Arenes. A One-Potortho-Borylation of Phenols, Arylamines, and Alkylarenes| journal = J. Am. Chem. Soc. | volume = 130 | issue = 24| pages = 7534–5 | doi = 10.1021/ja8015878 | pmid = 18494474 }} Selectivity for the ortho position in the case of using hydrosilyl directing groups has been attributed to reversible addition of the Si-H bond to the metal center, leading to preferential cleavage of the C–H bond ortho to the hydrosilyl substituent. Several other strategies to achieve ortho-borylation of arenes have been developed using various directing groups.{{cite journal | last1 = Ishiyama | first1 = T. | last2 = Miyaura | first2 = N. | last3 = Isou | first3 = H. | last4 = Kikuchi | first4 = T. | year = 2010 | title = Ortho-C–H borylation of benzoate esters with bis(pinacolato)diboron catalyzed by iridium–phosphine complexes| journal = Chem. Commun. | volume = 46 | issue = 1| pages = 159–61 | doi = 10.1039/b910298a | pmid = 20024326 | hdl = 2115/44631 | hdl-access = free}}{{cite journal | last1 = Kawamorita | first1 = S. | last2 = Ohmiya | first2 = H. | last3 = Hara | first3 = K. | last4 = Fukuoka | first4 = A. | last5 = Sawamura | first5 = M. | year = 2009 | title = Directed Ortho Borylation of Functionalized Arenes Catalyzed by a Silica-Supported Compact Phosphine−Iridium System| journal = J. Am. Chem. Soc. | volume = 131 | issue = 14| pages = 5058–9 | doi = 10.1021/ja9008419 | pmid = 19351202 }}Ros, A.; Estepa, B.; Lopez-Rodriquez, R.; Alvarez, E.; Fernandez, R.; Lassaletta, J.M. Angew. Chem. Int. Ed. 2011; 50, 1.

File:Directing groups for ortho borylation.jpg

A trisboryl iridium complex has been proposed to facilitate the mechanism for each of these reactions that result in C–H borylation of arenes and heteroarenes. Kinetic studies and isotopic labelling studies have revealed that an Ir(III) triboryl complex reacts with the arene in the catalytic process.Boller, T.M.; Murphy, J. M.; Hapke, M.; Ishiyama, T.; Miyaura, N.; Hartwig, J.F. J. Am. Chem. Soc. 2005;, 127, 14263.

A version of the catalytic cycle is shown below for the ortho borylation of hydrosilane compounds. Kinetic data show that an observed trisboryl complex coordinated to cyclooctene rapidly and reversibly dissociates cyclooctene to form a 16 electron trisboryl complex. In the case of using benzyldimethylsilane as a directing group it is proposed that benzyldimethylsilane reacts with the trisboryl iridium catalyst through reversible addition of the Si-H bond to the metal center, followed by selective ortho-C–H bond activation via oxidative addition and reductive elimination.{{cite journal | last1 = Boebel | first1 = T.A. | last2 = Hartwig | first2 = J.F. | year = 2008 | title = Silyl-Directed, Iridium-Catalyzedortho-Borylation of Arenes. A One-Potortho-Borylation of Phenols, Arylamines, and Alkylarenes| journal = J. Am. Chem. Soc. | volume = 130 | issue = 24| pages = 7534–7535 | doi = 10.1021/ja8015878 | pmid = 18494474}}

File:Mechanism of hydrosilane.jpg

Meta-selective borylation: Meta-selective C–H borylation is an important synthetic transformation, which was discovered in 2002 by Smith III from Michigan State University, USA. However, this meta borylation was completely sterically directed and was limited to only 1,3-disubstituted benzenes. Around 12 years later, Dr. Chattopadhyay and his team from Centre of Biomedical Research, U.P, India discovered an elegant technology for the meta-selective C–H bond activation and borylation. The team had shown that using the same substrate, one can switch the other positional selectivity just changing the ligand. The origin of the meta-selectivity was defined by the two parameter, such as: 1) electrostatic interaction, 2) a secondary B-N interaction.{{cite journal | last1 = Bisht | first1 = R. | last2 = Chattopadhyay | first2 = B. | year = 2016 | title = Formal Ir-Catalyzed Ligand-Enabled Ortho and Meta Borylation of Aromatic Aldehydes via in Situ-Generated Imines| doi = 10.1021/jacs.5b11683 | journal = J. Am. Chem. Soc. | volume = 138 | issue = 1| pages = 84–7 | pmid = 26692251 }}

At the same time, a team from Japan, Dr. Kanai reported an amazing concept for the meta-selective borylation based on the secondary interaction. This method covers various carbonyl compounds borylation.{{cite journal | last1 = Kanai | display-authors = etal | year = 2015 | title = A meta-selective C–H borylation directed by a secondary interaction between ligand and substrate| doi = 10.1038/nchem.2322 | journal = Nat. Chem. | volume = 7 | issue = 9| pages = 712–7| pmid = 26291942| bibcode = 2015NatCh...7..712K}}

In 1981, Hirao and co-workers have found that asymmetric reduction of prochiral aromatic ketones with chiral amino alcohols and borane afforded the corresponding secondary alcohols with 60% ee. They found out that the chiral amino alcohols would react with borane to form aloxyl-amine-borane complexes. The complexes are proposed to contain a relatively rigid five member-ring system which makes them thermal and hydrolytic stable and soluble in a wide variety of protic and aprotic solvents.{{cite journal|last=Hirao|first=Akira|author2=Itsuno, Shinichi |author3=Nakahama, Seiichi |author4= Yamazaki, Noboru |title=Asymmetric reduction of aromatic ketones with chiral alkoxy-amineborane complexes|journal=Journal of the Chemical Society, Chemical Communications|year=1981|issue=7|pages=315|doi=10.1039/c39810000315}}

File:CBS 1-uuu.tif

In 1987, Elias James Corey and co-workers found out that the formation of oxazaborolidines from borane and chiral amino alcohols. And the oxazaborolidines were found to catalyze the rapid and highly enantioselective reduction of prochiral ketones in the presence of BH3THF. This enantioselective reduction of achiral ketones with catalytic oxazaborolidine is called Corey–Bakshi–Shibata reduction or CBS reduction.{{cite journal|last=Corey|first=E. J.|author2=Bakshi, Raman K. |author3=Shibata, Saizo |title=Highly enantioselective borane reduction of ketones catalyzed by chiral oxazaborolidines. Mechanism and synthetic implications|journal=Journal of the American Chemical Society|date=September 1987|volume=109|issue=18|pages=5551–5553|doi=10.1021/ja00252a056}}{{cite journal|last=Corey|first=E. J.|author2=Bakshi, Raman K. |author3=Shibata, Saizo |author4=Chen, Chung Pin |author5= Singh, Vinod K. |title=A stable and easily prepared catalyst for the enantioselective reduction of ketones. Applications to multistep syntheses|journal=Journal of the American Chemical Society|date=December 1987|volume=109|issue=25|pages=7925–7926|doi=10.1021/ja00259a075}}

File:CBS 2-uuu.tif

In 1977, M. M. Midland and co-workers reported a surprising observation that B-3-alpha-Pinanyl-9-borabicyclo [3,3,1] nonane, readily prepared by hydroboration of (+)-alpha-pinene with 9-borobicyclo[3,3,1] nonane, rapidly reduces benzaldehyde-alpha-d to (S)-(+)-benzyl-alpha-d alcohol with an essentially quantitative asymmetric induction.{{cite journal|last=Midland|first=M.Mark|author2=Tramontano, Alfonso |author3=Zderic, Stephen A |title=The facile reaction of B-alkyl-9-borabicyclo[3.3.1]nonanes with benzaldehyde|journal=Journal of Organometallic Chemistry|date=July 1977|volume=134|issue=1|pages=C17–C19|doi=10.1016/S0022-328X(00)93625-8}}

File:MidLand1.tif

In the same year, M. M. Midland discovered B-3-alpha-pinanyl-9-BBN as the reducing agent, which could be easily available by reacting (+)-alpha-pinene with 9-BBN. The new reducing agent was later commercialized by Aldrich Co. under the name Alpine Borane and the asymmetric reduction of carbonyl groups with either enantiomer of Alpine-Borane is known as Midland Alpine-Borane reduction.{{cite journal|last=Midland|first=M. Mark|author2=Tramontano, Alfonso |author3=Zderic, Stephen A. |title=Preparation of optically active benzyl-.alpha.-d alcohol via reduction by B-3.alpha.-pinanyl-9-borabicyclo[3.3.1]nonane. A new highly effective chiral reducing agent|journal=Journal of the American Chemical Society|date=June 1977|volume=99|issue=15|pages=5211–5213|doi=10.1021/ja00457a068}}

In 2012, U. R. Y. Venkateswarlu and co-workers have reported a stereoselective method to synthesize pectinolide H. Midland reduction and Sharpless dihydroxylation reaction are involved in generating the three chiral centers at C–4’, C–5 and C–1’.{{cite journal|last=Ramesh|first=D.|author2=Shekhar, V. |author3=Chantibabu, D. |author4=Rajaram, S. |author5=Ramulu, U. |author6= Venkateswarlu, Y. |title=First stereoselective total synthesis of pectinolide H|journal=Tetrahedron Letters|date=March 2012|volume=53|issue=10|pages=1258–1260|doi=10.1016/j.tetlet.2011.12.122}}

File:Application of Midland reduction.tif

In 1993, N. A. Petasis and I. Akrltopoulou reported an efficient synthesis of allylic amines with a modified Mannich reaction. In this modified Mannich reaction, they have found that vinyl boronic acids can participate as nucleophiles to give geometrically pure allylamines. This modified Mannich reaction was known as Petasis boronic acid-Mannich Reaction.{{cite journal|last=Petasis|first=Nicos A.|author2=Akritopoulou, Irini|title=The boronic acid mannich reaction: A new method for the synthesis of geometrically pure allylamines|journal=Tetrahedron Letters|date=January 1993|volume=34|issue=4|pages=583–586|doi=10.1016/S0040-4039(00)61625-8}}{{cite journal|last=Yu|first=Tao|author2=Li, Hui |author3=Wu, Xinyan |author4= Yang, Jun |title=Progress in Petasis Reaction|journal=Chinese Journal of Organic Chemistry|year=2012|volume=32|issue=10|pages=1836|doi=10.6023/cjoc1202092|doi-access=free}}

File:PB 1.tif

In 1978, R. W. Hoffmann and T. Herold reported on the enantioselective synthesis of secondary homoallyl alcohols via chiral non-racemic allylboronic esters. The homoallylic alcohols were formed with excellent yield and moderate enantioselectivity.{{cite journal|last=Herold|first=Thomas|author2=Hoffmann, Reinhard W.|title=Enantioselective Synthesis of Homoallyl Alcoholsvia Chiral Allylboronic Esters|journal=Angewandte Chemie International Edition in English|date=October 1978|volume=17|issue=10|pages=768–769|doi=10.1002/anie.197807682}}

File:RA 1-uuu.tif

In 1985, W. R. Roush and co-workers found out that tartrate modified allylic boronates offer a simple, highly attractive approach to the control of facial selectivity in reactions with chiral and achiral aldehydes. In the following years, W.R. Roush and co-workers extended this strategy to the synthesis of but-2-ene-1,4-diols and anti-diols. This kind of reaction is known as Rouch asymmetric allylation.{{cite journal|last=Roush|first=William R.|author2=Walts, Alan E. |author3=Hoong, Lee K. |title=Diastereo- and enantioselective aldehyde addition reactions of 2-allyl-1,3,2-dioxaborolane-4,5-dicarboxylic esters, a useful class of tartrate ester modified allylboronates|journal=Journal of the American Chemical Society|date=December 1985|volume=107|issue=26|pages=8186–8190|doi=10.1021/ja00312a062}}{{cite journal|last=Roush|first=William R.|author2=Ando, Kaori |author3=Powers, Daniel B. |author4=Halterman, Ronald L. |author5= Palkowitz, Alan D. |title=Enantioselective synthesis using diisopropyl tartrate modified (E)- and (Z)-crotylboronates: Reactions with achiral aldehydes|journal=Tetrahedron Letters|date=January 1988|volume=29|issue=44|pages=5579–5582|doi=10.1016/S0040-4039(00)80816-3}}{{cite journal|last=Roush|first=William R.|author2=Grover, Paul T.|title=Diisopropyl tartrate (E)-γ-(dimethylphenylsilyl)allylboronate, a chiral allylic alcohol β-carbanion equivalent for the enantioselective synthesis of 2-butene-1,4-diols from aldehydes|journal=Tetrahedron Letters|date=January 1990|volume=31|issue=52|pages=7567–7570|doi=10.1016/S0040-4039(00)97300-3}}{{cite journal|last=Roush|first=William R.|author2=Gover, Paul T. |author3=Lin, Xiaofa |title=Diisopropyl tartrate modified (E)-γ-[(cyclohexyloxy)dimethylsilyl-allylboronate, a chiral reagent for the stereoselective synthesis of anti 1,2-diols via the formal α-hydroxyallylation of aldehydes|journal=Tetrahedron Letters|date=January 1990|volume=31|issue=52|pages=7563–7566|doi=10.1016/S0040-4039(00)97299-X}}

File:RA 2.tif

In 2011, R. A. Fernandes and P. Kattanguru have completed an improved total synthesis of (8S, 11R, 12R)- and (8R, 11R, 12R)-topsentolide B2 diastereomers in eight steps. In the paper, diastereoselective Roush allylation reaction was used as a key reaction in the total synthesis to introduce two chiral intermediate. And then the authors synthesized the two diastereomers through these two chiral intermediates.{{cite journal|last=Fernandes|first=Rodney A.|author2=Kattanguru, Pullaiah|title=Total synthesis of (8S,11R,12R)- and (8R,11R,12R)-topsentolide B2 diastereomers and assignment of the absolute configuration|journal=Tetrahedron: Asymmetry|date=November 2011|volume=22|issue=20–22|pages=1930–1935|doi=10.1016/j.tetasy.2011.10.020}}

File:Application of Roush allylation reaction.tif

In 1979, N. Miyaura and A. Suzuki reported the synthesis of arylated (E)-alkenes in high yield from aryl halides with alkyl-1-enylboranes and catalyzed by tetrakis(triphenylphosphine)palladium and bases. Then A. Suzuki and co-workers extend this kind of reaction to other organoboron compounds and other alkenyl, aryl, alkyl halides and triflate. The palladium-catalyzed cross-coupling reaction organoboron compounds and these organic halides to form carbon-carbon bonds are known as Suzuki–Miyaura cross-coupling.{{cite journal|last=Miyaura|first=Norio|author2=Suzuki, Akira|title=Stereoselective synthesis of arylated (E)-alkenes by the reaction of alk-1-enylboranes with aryl halides in the presence of palladium catalyst|journal=Journal of the Chemical Society, Chemical Communications|year=1979|issue=19|pages=866|doi=10.1039/C39790000866}}{{cite journal|last=Miyaura|first=Norio|author2=Yamada, Kinji |author3=Suzuki, Akira |title=A new stereospecific cross-coupling by the palladium-catalyzed reaction of 1-alkenylboranes with 1-alkenyl or 1-alkynyl halides|journal=Tetrahedron Letters|date=January 1979|volume=20|issue=36|pages=3437–3440|doi=10.1016/S0040-4039(01)95429-2|hdl=2115/44006|url=http://eprints.lib.hokudai.ac.jp/dspace/bitstream/2115/44006/1/tetrahedronletters1979.pdf|hdl-access=free}}

File:Suzuki 1.tif

In 2013, Joachim Podlech and co-workers determined the structure of Alternaria mycotoxin altenuic acid III by NMR spectroscopic analysis and completed its total synthesis. In the synthetic strategy, Suzuki-Miyaura Cross-Coupling reaction was used with a highly functionalized boronate and butenolides to synthesize a precursor of the natural product in high yield.{{cite journal|last=Nemecek|first=Gregor|author2=Thomas, Robert |author3=Goesmann, Helmut |author4=Feldmann, Claus |author5= Podlech, Joachim |title=Structure Elucidation and Total Synthesis of Altenuic Acid III and Studies towards the Total Synthesis of Altenuic Acid II|journal=European Journal of Organic Chemistry|date=October 2013|volume=2013|issue=28|pages=6420–6432|doi=10.1002/ejoc.201300879}}

File:Application of Suzuki Reaction.tif

In 1904, Fritz Ullmann found out that copper powder could significantly improve the reaction of aryl halides with phenols to give biaryl ethers. This reaction is known as Ullmann condensation. In 1906, I. Goldberg extended this reaction to synthesize an arylamine by reacting aryl halides with an amide in the presence of Potassium Carbonate and CuI. This reaction is known as Goldberg modified Ullmann condensation.{{cite book|last=Kürti|first=László|title=Strategic applications of named reactions in organic synthesis : background and detailed mechanisms ; 250 named reactions|url=https://archive.org/details/strategicapplica00kurt_573|url-access=limited|year=2007|publisher=Elsevier Academic Press|location=Amsterdam [u.a.]|isbn=978-0-12-429785-2|pages=[https://archive.org/details/strategicapplica00kurt_573/page/n515 464]–465|edition=Pbk. ed., [Nachdr.].|author2=Czakó, Barbara}} In 2003, R. A. Batey and T. D. Quach have modified this kind of reactions by using potassium organotrifluoroborates salts to react with aliphatic alcohols, aliphatic amines or anilines to synthesize aryl ethers or aryl amines.{{cite journal|last=Quach|first=Tan D.|author2=Batey, Robert A.|title=Copper(II)-Catalyzed Ether Synthesis from Aliphatic Alcohols and Potassium Organotrifluoroborate Salts|journal=Organic Letters|date=April 2003|volume=5|issue=8|pages=1381–1384|doi=10.1021/ol034454n|pmid=12688764}}{{cite journal|last=Quach|first=Tan D.|author2=Batey, Robert A.|title=Ligand- and Base-Free Copper(II)-Catalyzed C−N Bond Formation: Cross-Coupling Reactions of Organoboron Compounds with Aliphatic Amines and Anilines|journal=Organic Letters|date=1 November 2003|volume=5|issue=23|pages=4397–4400|doi=10.1021/ol035681s|pmid=14602009}}

File:MU 1.tif

• Organoboron chemistry
• Reactions of organoborates and boranes
• Corey–Itsuno reduction
• Midland Alpine borane reduction
• Petasis reaction
• Suzuki reaction
• Boryl radicals

{{reflist|30em}}

Category:Boron

Category:Chemical reactions