Synthesis of Seven-Membered Cyclic Enol Ether Derivatives from the Reaction of a Cyclic Phosphonium Ylide with α,β-Unsaturated Esters

Abstract

The tandem Michael−intramolecular Wittig reactions of a five-membered cyclic phosphonium ylide (2) with α,β-unsaturated esters afforded seven-membered cyclic enol ether derivatives 4a − e in 37−73% yield. The reaction proceeded via a rigid phosphabicyclic intermediate and supplied the enol ether derivatives with high stereoselectivity. On the other hand, the reaction using ethyl acrylate as a substrate gave the 1:3 adduct 15 of the ylide and the enoate via the repetition of the Michael-type addition and regeneration of the ylide followed by the intramolecular Wittig reaction.

Design and synthesis of new azetidine‐steroid derivative with inotropic activity in a heart failure model

“…Therefore, in this investigation, four azetidine-steroid derivatives were synthesized to evaluate their inotropic activity using a heart failure model. The first stage was achieved via preparation of an ether-steroid derivative (figure 1); it is important to mention that there are several methods for the preparation of ether groups which involve a series of reagents such as Me3SiCN, [25] K2CO3/acetone, [26] tetrahydrofuranlithium-aluminum hydride, [27] Me3SiCl, [28] K3PO4-DMF, [29] ethyl cinnamate [30] and others. In this investigation, an ether-steroid derivative (2) was prepared from estrone and p-nitrobenzoyl azide in the presence of dimethyl sulfoxide.…”

Tandem transformations initiated and determined by the Michael reaction

“…76 The tandem Michael and Wittig reactions involving fivemembered phosphonium ylides 200 and a,b-unsaturated esters gave rise to seven-membered vinyl ethers 201. 77 The process occurred via the structurally rigid phosphorus-containing bicyclic intermediate A which provided high stereoselectivity of the formation of vinyl ethers. Analogous reactions were observed in the case of a,bunsaturated thioesters 78 yielding cycloheptene derivatives 202.…”

Domino Reaction of Pyrrolidinium Ylides: Michael Addition/[1,2]-Stevens Rearrangement

“…Domino reactions provide an opportunity to synthesize in one step relatively complicated products from simple precursors. − Many well-known domino transformations are initiated by the Michael-type addition. ,− Among anions undergoing a conjugate addition to electrophilic alkenes are sulfonium, ,− sulfoxonium, ,, arsonium, − ,, telluronium, ,,, phosphonium, ,, pyridinium, , and ammonium ,,,, ylides, generated from respective salts upon treatment with a base. The anionic intermediates thus formed usually take part in Michael-initiated ring-closure (MIRC) reactions, affording cyclopropanes or undergoing other transformations, ,,− , giving unexpected products, − mainly dihydrofuran and benzofuran derivatives. ,,,,− …”