Carbon-Carbon Bond Cleavage of .ALPHA.-Hydroxybenzylheteroarenes Catalyzed by Cyanide Ion: Retro-Benzoin Condensation Affords Ketones and Heteroarenes and Benzyl Migration Affords Benzylheteroarenes and Arenecarbaldehydes.
4-(α-Benzyl-α-hydroxybenzyl)quinazoline (4a) underwent retro-benzoin condensation catalyzed by cyanide ion to give deoxybenzoin (2a) and quinazoline (5a). Similarly, several nitrogen-containing heteroarenes (4, 9, 12, 16-19) having an α-hydroxybenzyl group at the α-position of the nitrogen underwent retro-benzoin type condensation to afford ketones (2) and heteroarenes (5). However, similar reaction of pyrazolopyrimidines (13, 14, 15) having an α-benzyl-α-hydroxybenzyl group resulted in benzyl migration, giving benzylpyrazolopyrimidines (8) and arenecarbaldehydes (3). Tetrabutylammonium cyanide (11, Bu4NCN) was a more effective cyanide ion donor than KCN (10). The retro-benzoin condensation was applied to the synthesis of 2-substituted quinazolines (38) from 2-chloro-4-aroylquinazolines (34), using the aroyl group as a protecting and electron-withdrawing group.
An iron-catalyzed aerobic oxidation of (alkyl)(aryl)azinylmethanes has been developed leading to tertiary alcohols in moderate to good yields. Hock rearrangement was identified as a major side reaction leading to a complex mixture of undesired products. Addition of thiourea sometimes allows inhibiting this side reaction and steers the reaction towards the desired products.
Pyridine-Directed Organolithium Addition to an Enol Ether
作者:Jingyue Yang、Gregory B. Dudley
DOI:10.1002/adsc.201000495
日期:2010.12.17
reported anionic rearrangement of benzyl 2-pyridyl ethers can now be accessed by a distinct and unusual mechanism: addition of alkyllithium reagents to α-(2-pyridyloxy)-styrene triggers an anionic rearrangement to afford tertiary pyridyl carbinols. The process is explained by invoking a contra-electronic, pyridine-directed carbolithiation of the enolether π-system.
system involving Er(III)-based chiral Lewisacid catalysis, Ir(III)-based photoredox catalysis, and bromide-radical-mediated hydrogen atom transfer. The introduction of a bulky and nonredox chiral Lewisacid through the photoredox pathway enables the radical addition process and inhibits the above competitive reactions. The visible-light-promoted catalytic asymmetric alkylation of heteroaryl-based ketones
A highlyefficient photoinduced iron-catalyzed method has been developed for the direct use of alcohols as surrogates for organometallic reagents in the synthesis of tertiaryalcohols. This method can be applied to both primary and secondaryalcohols with diverse structures, enabling their reaction with aryl ketones under mild conditions. A variety of functional groups, including those that are typically