The (4+3)-cycloaddition reaction: heteroatom-substituted allylic cations as dienophiles

Abstract

The (4+3)-cycloaddition of allylic cations to dienes is a powerful method for the direct synthesis of seven-membered rings. Recent developments in this area have included new methods for the generation of allylic cations, diastereoselective and catalytic, enantioselective reactions, an increased understanding of the diverse mechanistic possibilities of the reaction and applications to the total synthesis of natural products and their analogues.

Rh-Catalyzed (5+2) Cycloadditions of 3-Acyloxy-1,4-enynes and Alkynes: Computational Study of Mechanism, Reactivity, and Regioselectivity

“…1 In contrast to the facile synthetic routes to five- and six-membered rings, efficient cycloaddition strategies to form seven-membered rings, such as (5+2) and (4+3) reactions, are still limited. 2 In 1995, Wender group reported the first transition metal-catalyzed (5+2) cycloadditions employing vinylcyclopropanes (VCPs) as the five-carbon synthon. This methodology has evolved to a general and effective route to seven-membered rings.…”

Recent developments in gold-catalyzed cycloaddition reactions

“…Based on these and other reports demonstrating the ability of gold(I) and platinum(II) catalysts to induce reactions of allenes through cationic intermediates [91–94], we investigated the possibility of using allenes as allyl cation surrogates, such that they could participate in concerted [4C(4π) + 3C(2π)] cycloadditions with conjugated dienes, a similar process to those previously reported between oxyallyl cations and dienes [95–96]. Initially, we found that PtCl 2 was an excellent catalyst for promoting these intramolecular [4C + 3C] cycloadditions between 1,3-dienes and allenes (Scheme 26) [97].…”

Gold(I)-catalyzed enantioselective cycloaddition reactions

“…Early in 2008, our group demonstrated the possibility of using gold-activated allenes as allyl cation surrogates capable of participating in concerted [4C(4π) + 3C(2π)] cycloadditions with conjugated dienes [54], a process related to the classical oxyallyl cation [4 + 3] cycloadditions [55–57]. An initial screening demonstrated that PtCl 2 was a good catalyst for promoting these intramolecular [4C + 3C] cycloadditions [54].…”