Tatsuo Ishiyama

SYNTHESIS OF ARYLBORONATES VIA THE PALLADIUM(0)-CATALYZED CROSS-COUPLING REACTION OF TETRA(ALKOXO)DIBORONS WITH ARYL TRIFLATES

Abstract The cross-coupling reaction of (RO)2BB(OR)2 (RO =methoxo and pinacolato) with aryl triflates to give arylboronates was carried out at 80 °C in the presence of PdCl2(dppf) (3 mol%), dppf (3 mol%) and KOAc (3 equivs) in dioxane. The reaction was available with various functional groups such as nitro, cyano, ester, and carbonyl groups.

Chemistry of Group 13 element-transition metal linkage — the platinum- and palladium-catalyzed reactions of (alkoxo)diborons

Abstract The metal-catalyzed borylation of alkenes, alkynes, and organic electrophiles with BB compounds was developed for the synthesis of organoboronic esters from simple organic substrates. The platinum(0)-catalyzed addition of bis(pinacolato)diboron to alkenes and alkynes stereoselectively yielded cis -bis(boryl)alkanes or cis -bis(boryl)alkenes. The addition of diboron to 1,3-dienes with a platinum(0) complex afforded a new access to the cis -1,4-bis(boryl)butene derivatives which are a versatile reagent for diastereoselective allylboration of carbonyl compounds. The cross-coupling reaction of diborons with aryl and vinyl halides or triflates, and allyl chlorides or acetates was found to yield aryl-, vinyl-, and allylboronates in high yields in the presence of a base and a palladium catalyst, which provides the first one-step procedure for the synthesis of organoboronic esters from organic electrophiles. The mechanisms and the synthetic applications of these reactions are discussed.

A borylcopper species generated from bis(pinacolato)diboron and its additions to α,β-unsaturated carbonyl compounds and terminal alkynes

Abstract The addition of bis(pinacolato)diboron [(Me4C2O2)B–B(O2C2Me4)] to α,β-unsaturated carbonyl compounds giving β-boryl carbonyl compounds and the addition to terminal alkynes yielding either 2-boryl-1-alkenes or 1-boryl-1-alkenes were carried out in DMF at room temperature in the presence of CuCl and AcOK. The transmetalation between diboron and [Cu(Cl)OAc]K generating a borylcopper species was proposed as the key step in the reactions because CuOAc similarly mediated both addition reactions to enones and alkynes in the presence of LiCl.

Iridium-catalyzed C–H coupling reaction of heteroaromatic compounds with bis(pinacolato)diboron: regioselective synthesis of heteroarylboronates

The C–H coupling of aromatic heterocycles with bis(pinacolato)diboron was carried out in octane at 80–100°C in the presence of a 1/2[IrCl(COD)]2-(4,4′-di-tert-butyl-2,2′-bipyridine) catalyst (3 mol%). The reactions of five-membered substrates such as thiophene, furan, pyrrole, and their benzo-fused derivatives exclusively produced 2-borylated products, whereas those of six-membered heterocycles including pyridine and quinoline selectively occurred at the 3-position. Regioselective synthesis of bis(boryl)heteroaromatics was also achieved by using an almost equimolar amount of substrates and the diboron.

Transition metal-catalyzed borylation of alkanes and arenes via CH activation

Abstract Since 1999, direct borylation of hydrocarbons catalyzed by a transition metal complex has been extensively studied by several groups and has become an economical, efficient, elegant, and environmentally benign protocol for the synthesis of a variety of organoboron compounds. Re-, Rh-, Ir- and Pd-catalyzed CH borylation of alkanes, arenes and benzylic positions of alkylarenes by bis(pinacolato)diboron or pinacolborane provide alkyl-, aryl-, heteroaryl- and benzylboron compounds, respectively. In this review, seminal early works and exciting recent developments in the area of direct borylation of hydrocarbons via CH activation are summarized.

Synthesis of unsymmetrical biaryl ketones via palladium-catalyzed carbonylative cross-coupling reaction of arylboronic acids with iodoarenes

Abstract The cross-coupling reaction between arylboronic acids, carbon monoxide (1 atm), and aryl iodides in the presence of palladium catalyst and base provided unsymmetrical biaryl ketones in high yields. The choice of a suitable base and solvent was essential to achieve selective formation of the unsymmetrical biaryl ketone without a biaryl by-product.

Palladium-catalyzed cross-coupling reactions of B-alkyl-9-BBN or trialkylboranes with aryl and 1-alkenyl halides

Abstract The reactions of trialkylboranes or B-alkyl-9-BBN with aryl and 1-alkenyl halides take place readily in the presence of PdCl2(dppf) and sodium hydroxide or methoxide to afford alkylated arenes and alkenes in excellent yields.

A synthesis of allylboronates via the palladium(0)-catalyzed cross-coupling reaction of bis(pinacolato)diboron with allylic acetates

Abstract The cross-coupling reaction of bis(pinacolato)diboron [(Me 4 C 2 O 2 )BB(O 2 C 2 Me 4 )] with allyl acetates regio- and E-stereoselectively provided the pinacol esters of allylboronic acids in high yields. The reaction was efficiently catalyzed by Pd(dba) 2 in DMSO at 50 °C.

Platinum(0)-catalyzed diboration of allenes with bis(pinacolato)diboron

Addition of bis(pinacolato)diboron [(Me4C2O2)BB(O2C2Me4)] to various allenes was carried out in excellent yields in the presence of Pt(PPh3)4 at 80 °C or Pt(dba)2(c-Hex)3P at 50 °C. The addition to internal double bond was predominant for monosubstituted allenes, whereas the terminal diboration products were regioselectively obtained when a sterically bulky phosphine ligand of (c-Hex)3P and 1,1-disubstituted allenes were used.

Palladium-catalyzed carbonylative cross-coupling reaction of iodoalkanes with 9-alkyl-9-BBN derivatives. A direct and selective synthesis of ketones

Abstract The synthesis of unsymmetrical ketones by means of the palladium-catalyzed carbonylative cross-coupling reaction of 9-alkyl-9-BBN derivatives with iodoalkanes under a carbon monoxide atmosphere is described.