A Michael Equilibration Model To Control Site Selectivity in the Condensation toward Aminopyrazoles.

A Michael equilibration model is presented to provide for site-selective pyrazole condensations between alkoxyacrylonitriles and hydrazines. Both pyrazole isomers were accessed with high selectivity by employment of kinetically or thermodynamically controlled conditions. Substrate scope and identification of Michael intermediates, as well as competitive pathways, support the presented mechanistic proposal.

One-step formation of fused tetracyclic skeletons from cyclohexene-diynes and carbon monoxide through Rh(I)-catalyzed [2 + 2 + 2 + 1] cycloaddition reaction.

Rapid construction of 5-7-6-5 fused tetracyclic carbocycles and heterocycles from cyclohexene-diynes and CO has been achieved in one step through a Rh(i)-catalyzed [2 + 2 + 2 + 1] cycloaddition process.

Direct synthesis of monofunctionalized indolizine derivatives bearing alkoxymethyl substituents at C-3 and their benzofused analogues.

[reaction: see text] Treatment of (Z)-2-pyridine and quinoline silylated vinylacetylenes at reflux with several alcohols in the presence of a suitable inorganic base (KOH, K2CO3, CsF, or KF) serendipitously gave 3-alkoxylmethylindolizines and the corresponding 1-alkoxymethylpyrrolo [1,2-a]quinolines and not the anticipated desilylated vinylacetylene derivatives. A mechanistic possibility for this unexpected chemical transformation is suggested.

Practical synthesis of (Z)-polyaromatic and heteroaromatic vinylacetylenes.

[reaction: seet text] Two synthetic routes to several (Z)-polyaromatic and heteroaromatic substituted vinylacetylenes are described. The nature of aryl- or heteroaryl-substituted carboxaldehyde used as starting material dictated the choice of Wittig salt employed. A very attractive way to construct polyaromatic and pyridine-containing enynes is the reaction of polyaromatic and pyridine-containing aldehydes with bromomethyltriphenylphosphonium bromide in the presence of potassium tert-butoxide followed by a Sonogashira desilylation procedure (method B).