The Palladium‐Catalyzed Addition of Organoboronic Acids to Alkynes

Abstract

No base is necessary: Excellent yields are produced on addition of organoboronic acids to alkynes under mild reaction conditions when palladium compounds are used as catalysts (see scheme). Unlike the Suzuki‐type cross‐coupling reaction, the current reaction occurs in an acidic medium.

Synthesis of 1,3-Substituted Cyclobutanes by Allenoate-Alkene [2 + 2] Cycloaddition

“…Spectral data were consistent with literature-reported values. 35 1 H NMR (400 MHz, CDCl 3 ) δ 7.54–7.28 (m, 10H), 5.49 (d, J = 5.7 Hz, 2H). 13 C NMR (100 MHz, CDCl 3 ) δ 150.2, 141.6, 128.4, 128.3, 127.8, 114.4.…”

Palladium-catalyzed hydroarylation of alkynes with arylboronic acids

“…Subsequently, the effects of bases and solvents were evaluated (entries 10-16). We found that potassium carbonate and cesium carbonate are both suitable bases, but some other bases such as NaOH and Et 3 N are ineffective (entries [10][11][12], THF is the best solvent among the solvents examined, and no reaction occurred in alcohol (entries [14][15][16]. It should be noted that both palladium and bases are necessary, no 3ab was given in the absence of bases and palladium catalysts (entries 13 and 17).…”

“…6,7 Then, the nickel-catalyzed 8 selective synthesis of multi-substituted aryl-alkenes and aryl-dienes, copper-catalyzed 9a conjugate additions of alkynoates with arylboronic acid, cobaltcatalyzed 9b similarly regio-and stereoselective transformation as well as palladium-catalyzed hydroarylation reaction of alkyne have been reported soon after that. 10,11 However, palladium-catalyzed approaches for hydroarylation of sterically hindered or electron-deficient substrates often gave poor yields and the regioselectivity of the addition of organometallics to alkynes still need to be improved. Especially, all of reported Pd-catalyzed hydroarylation of alkynes with arylboron must be proceeded in the present of acetic acid as additive, 10,11 thereby, to some extent, the reaction is confined to acid-compatible substrates and equipments.…”

“…10,11 However, palladium-catalyzed approaches for hydroarylation of sterically hindered or electron-deficient substrates often gave poor yields and the regioselectivity of the addition of organometallics to alkynes still need to be improved. Especially, all of reported Pd-catalyzed hydroarylation of alkynes with arylboron must be proceeded in the present of acetic acid as additive, 10,11 thereby, to some extent, the reaction is confined to acid-compatible substrates and equipments.…”

Catalytic Tandem Organic Sequences through Selective Boron Addition Chemistry

“…The yield and enantioselectivity of rhodium-catalyzed asymmetric cyclization/hydroboration of 1,6-enynes were therefore optimized when catecholborane was the hydroborating reagent and (S)-Binap was the chiral ligand, (Scheme 19), [34]. Fur-ther formation of a Pd hydride species by protonation with the alcohol followed by insertion of the alkyne into the Pd-H bond accounts for the observed alkene stereochemistry [36], (Scheme 22, path a). This method tolerated alkyl or aryl substitution at the alkyne carbon atom and gemdialkyl substitution at either the propargylic or allylic position.…”