A continuous Michael and aldol coupling of α,β-enones catalyzed by iridium complexes
摘要:
Ir[(COD)(PPh3)(2)]OTf activated by H-2 molecule catalyzes Michael-type coupling of alpha,beta-enones with enoxysilanes to give 1,5-dicarbonyl compounds after the subsequent protodesilylation. An identical catalyst system makes it possible to attain a continuous Michael and aldol modification toward alpha,beta-enones in a one-pot operation. (C) 2000 Elsevier Science Ltd. All rights reserved.
Generation of a novel type of organotin enolate has been accomplished by the regioselective ring cleavage of diketene with bis(tributyltin) oxide; the enolate afforded the first example of Michael addition in reactions using organotin(IV) enolates.
Δ3-Dihydropyrans and tetrahydropyrans by reduction of pyrylium salts with sodium borohydride in acetic acid
作者:Teodor-Silviu Balaban、Alexandru T Balaban
DOI:10.1016/s0040-4039(00)95365-6
日期:1987.1
major reduction products with triacetoxyborohydride (NaBH4 in AcOH) of 2,4,6-trisubstituted pyrylium salts bearing alkyl substituents in the 2- and/or 6- position are the Δ3-dihydropyrans with 2- and 6- substituents and the all--2,4,6-trisubstituted tetrahydropyrans. Δ3-Dihydropyrans are shown to be formed 2H-pyrans by a 1,4 reduction while tetrahydropyrans result from 4H-pyrans by reduction of both