Efficient Activation of Acetals, Aldehydes, and Imines toward Silylated Nucleophiles by the Combined Use of Catalytic Amounts of [Rh(COD)Cl]<sub>2</sub>and TMS-CN under Almost Neutral Conditions
In the presence of a catalytic amount of a transition metal compound such as [Rh(COD)Cl]2, Co(acac)2, or NiCl2, trimethylsilyl cyanide smoothly reacts with acetals to form α-methoxy carbonitriles in good yields. In the coexistence of catalytic amounts of [Rh(COD)Cl]2 and TMS-CN, silyl enol ethers or ketene silyl acetals react with acetals, aldehyes, or imines to yield the corresponding coupling products in good yields under almost neutral conditions.
An easy access to bioactive 13-hydroxylated and 11,13-dihydroxylated sesquiterpene lactones (SLs) through Michael addition of a nucleophilic hydroxyl group
作者:Francisco A. Macías、María D. García-Díaz、Guillermo M. Massanet、José F. Gómez-Madero、Frank R. Fronczek、Juan C.G. Galindo
DOI:10.1016/j.tet.2008.09.024
日期:2008.12
The addition of a hydroxyl group to α,β-unsaturated carbonyl systems provides a new and easy access to bioactive difunctionalized sesquiterpene lactones (SLs) through a Michael addition to the α-methylene-γ-lactone system. The use of HMPA to enhance the nucleophilic properties of the hydroxyl groups and to stabilize the enolate is discussed. Also, we present a proposal for the mechanism based on the
Alkali metal hydride or aqueous hydroxide induced conjugate addition of trimethylsilyl enol ethers to enones. A convenient alternative to Lewis acid mediated reaction
作者:Vishwanath M. Swamy、Amitabha Sarkar
DOI:10.1016/s0040-4039(97)10771-7
日期:1998.3
Conjugate addition to enones by enolates derived from base-induced cleavage of OSi bond of trimethylsilyl enol ethers, yields 1,5-dicarbonyl compounds in good yields.
Efficient and environmentally friendly synthesis of chalcones and 2,6-bis(arylmethylidene)cycloalkanones was carried out by aldol condensation of ketones with aromatic aldehydes in water in the presence of polyethylene glycol 400.
The porcine pancreas lipase (PPL) type II catalyzes the aminolysis of benzylidene malonates by regiospecific amidation of substrates and afforded the Z-isomer; no E-isomer or diamide byproducts were observed. PPL also catalyzes Michael addition of acetophenone to various derivatives of chalcones.