Pericyclic reactions in nature: Synthesis and Cope rearrangement of thermolabile bis-alkenylcyclopropanes from female gametes of marine brown algae (Phaeophyceae)
摘要:
The biosyntheses of the 6-substituted cyclohepta-1,4-dienes dictyotene (1), ectocarpene (2), desmarestene (3), vinylcycloheptadiene (4) and lamoxirene (5) involve a spontaneous Cope rearrangement of thermolabile bis-alkenylcyclopropane precursors like 16, 10, 26 and 30. The unstable precursors and the rearranged cycloheptadienes were synthesised from the chiral 2-iodovinylcyclopropane 12 using Pd-0 or Cu-1 catalysed approaches. Activation parameters of the Cope rearrangements were determined. Bioassays with pre-ectocarpene 10 established the thermolabile cyclopropane (1R,2R)-10, rather than the cyclohepta-1,4-diene(6S)-2, as the genuine pheromone of the brown alga Ectocarpus siliculosus. (C) 1997 Elsevier Science Ltd.
Secondary deuterium kinetic isotope effects at the termini of cis-1,2-divinylcyclopropane and cis-1,2-divinylcyclobutane in their 3,3-sigmatropic shifts: evidence for different transition-state structures
Cascade Cope/Winstein Rearrangements: Synthesis of Azido-Cycloheptadienes from Dialkenylcyclopropanes Possessing a Vinyl Azide
作者:Thomas Abegg、Janine Cossy、Christophe Meyer
DOI:10.1021/acs.orglett.2c01888
日期:2022.7.15
2-Dialkenylcyclopropanes incorporating a vinyl azide, generated by Knoevenagel condensations between the corresponding cyclopropanecarbaldehydes and α-azido ketones, undergo cascade Cope and Winstein [3,3]-sigmatropic rearrangements, under mild conditions. The sequence allows access to diversely substituted 1,4-cycloheptadienes armed with a secondary allylic azide with up to three stereocenters.