A New Method of Synthesizing Deoxybenzoins from 1,3-Dimethyl-2-(.ALPHA.-benzyloxybenzyl)imidazolium and 1,3-Dimethyl-2-(.ALPHA.-benzyloxybenzyl)benzimidazolium Iodides Based on Wittig-Type Rearrangement.
Palladium-Catalyzed Mono-α-arylation of Carbonyl-Containing Compounds with Aryl Halides using DalPhos Ligands
作者:Sarah M. Crawford、Pamela G. Alsabeh、Mark Stradiotto
DOI:10.1002/ejoc.201200951
日期:2012.10
We report the extension and optimization of the [Pd(cinnamyl)Cl]2/DalPhos catalyst system, previously found effective for the mono-α-arylation of acetone, to the mono-α-arylation of a variety of carbonyl-containing compounds with aryl halides and heteroaryl halides. Aryl methyl ketones, heteroaryl methyl ketones, propiophenones, malonates, and methoxyacetone can be α-arylated under relatively mild
One-pot synthesis of useful heterocycles in medicinal chemistry using a cascade strategy
作者:Guiyong Wu、Weiyu Yin、Hong C. Shen、Yong Huang
DOI:10.1039/c2gc16457d
日期:——
To access useful heterocycles in medicinal chemistry such as pyridazinones, dihydropyrimidinones, and dihydropyrimidinthiones, a “green” mild and highly efficient one-pot triple cascade was developed involving a Claisen–decarboxylation, electrophilic reaction, and subsequent heterocyclization. In addition, indazoles and benzofurans could also be constructed via a double cascade. To develop the cascade process, a direct Claisen–decarboxylation reaction was firstly optimized. This reaction can then couple with electrophilic reactions including alkylation, Michael addition or aldol reaction to enable the preparation of various aryl ketones in a one-pot fashion.
Potassium enolates of alkyl aryl ketones react selectively in DMSO with phenylazo 1a and 4-methylphenylazo tert-butyl sulfide 1b undergoing respectively effective α-phenylationvia SRN1 and α-(4-methylphenyl)hydrazonylation via elimination-addition.
A New Method of Synthesizing Deoxybenzoins from 1,3-Dimethyl-2-(.ALPHA.-benzyloxybenzyl)imidazolium and 1,3-Dimethyl-2-(.ALPHA.-benzyloxybenzyl)benzimidazolium Iodides Based on Wittig-Type Rearrangement.
The treatment of 1, 3-dimethyl-2-(α-benzyloxybenxyl)benzimidazolium iodides 1 with a base gave deoxybenzoins 2 in moderate yields. Sodium hydride (NaH), potassium carbonate (K2CO3), and cesium carbonate (Cs2CO3) were effective bases in this reaction. Deoxybenzoins 2 were produced through rearrangement of the benzyl group followed by expulsion of the 1, 3-dimethylbenzimidazolium ylide (A). The rearrangement proceeds in a way similar to Witting rearrangement. Deoxybenzoins 2 were also formed in good yields from 1, 3-dimethyl-2-(α-benzyloxybenxyl)-imidazolium iodides 4 upon similar treatment. However, the quaternary salts having a thiazolium moiety 5a and a pyridinium moiety 6a failed to produce deoxybenzoin (2a).