Silane-Promoted Cycloisomerization of Functionalized 1,6-Dienes Catalyzed by a Cationic (π-Allyl)palladium Complex
摘要:
[GRAPHICS]A 1:1 mixture of the (pi-allyl)palladium complex (eta(3)-C3H5)Pd(Cl)PCy3 and NaB[3,5-C6H3(CF3)(2)](4) in the presence of HSiEt3 catalyzed the cycloisomerization of functionalized 1,6-dienes to form 1,2-disubstituted cyclopentenes in good yield with high selectivity (typically >94%). The protocol tolerated a range of functional groups and substitution at one of the allylic carbon atoms.
Regioselective rhodium-catalyzed allylic alkylation/ring-closing metathesis approach to carbocycles
作者:P.Andrew Evans、Lawrence J Kennedy
DOI:10.1016/s0040-4039(01)01467-8
日期:2001.10
Treatment of the allylic carbonates 1a–c with the sodium anion of the α-substituted malonates (n=0–2) and Wilkinson's catalyst modified with a triorganophosphite, furnished the allylic alkylation products 2/3a–i in 83–97% yield, favoring 2a–i. The dienes 2a–i were then subjected to ring-closing metathesis using either I or II, to afford the carbocycles 4a–i in 79–99% yield.
Development, Synthetic Scope, and Mechanistic Studies of the Palladium-Catalyzed Cycloisomerization of Functionalized 1,6-Dienes in the Presence of Silane
作者:Philip Kisanga、Ross A. Widenhoefer
DOI:10.1021/ja001730+
日期:2000.10.1
A 1:1 mixture of the pi-allyl palladium complex (eta (3)-C3H5)Pd(CI)PCy3 Cia) and NaB[3,5-C6H3(CF3)(2)](4) in the presence of HSiEt3 catalyzed the cycloisomerization of diethyl diallylmalonate (2b) to form 4,4-dicarbomethoxy 1,2-dimethylcyclopentane (3b) in 98% yield with 98% isomeric purity. The procedure tolerated a range of functionality including esters, ketones, sulfones, protected alcohols, and substitution at the allylic and terminal olefinic carbon atoms. Cycloisomerization of 2b obeyed zero-order kinetics to >3 half-lives with initial formation of 1,1-dicarboethoxy-4-methyl-3-methylenecyclopentane (4b), followed by secondary isomerization to 3b. Deuterium labeling studies revealed that the conversion of 2b to 4b was accompanied by significant H/D exchange, consistent with an addition/elimination pathway coupled with facile H/D exchange of the Pd-H(D) intermediates with free silane.