The efficient synthesis of indolo[2,3-alpha]quinolizin-4-ones 2 is described in two steps via formal [3 + 3] cycloaddition reaction of alpha-sulfonyl tryptaminylacetamide 4 with various alpha, beta-unsaturated esters 5 and the regioselective reduction of the resulting glutarimides 3 with sodium borohydride then sequent further dehydrated cyclization in the presence of boron trifluoride etherate. The useful building block is applied to synthesize deplancheine (1a) and yohimbane (1b). (C) 2004 Elsevier Ltd. All rights reserved.
GASSMAN, PAUL G.;LEE, CHANGJIN, TETRAHEDRON LETT., 30,(1989) N7, C. 2175-2178
作者:GASSMAN, PAUL G.、LEE, CHANGJIN
DOI:——
日期:——
Copper-catalyzed, stereoconvergent, cis-diastereoselective borylative cyclization of ω-mesylate-α,β-unsaturated esters and ketones
stereoconvergent borylative cyclization of ω-mesylate-α,β-unsaturated compounds is facilitated by a simple Cu-bisphosphine catalyst. This reaction provides a novel route to cis-β-boron-substituted five- and six-memberedcarbocycle and heterocycle esters. Mechanistic studies indicate that stereoconvergence and cis-substitution likely stem from the rapid enolation of the borylcopper adduct with the substrate