Laser-powered decomposition of spiro[2.n]alkanes (n = 2-5)
摘要:
The laser heating of spiro[2.n]alkanes (n = 2-5) and of their 1,1,2,2-tetradeuterated isotopomers reveals dissimilar modes of their thermal decomposition. Spiropentane decomposes into ethene and propadiene via two competing routes: the direct cleavage and the more important cleavage via intermediary methylenecyclobutane. Spirohexane decomposes through two important concurrent pathways which are the expulsions of ethene from the three-membered ring and a more feasible expulsion of ethene from the four-membered ring. Spiroheptane and spirooctane decompose by a radical-chain mechanism and afford complex mixtures of products; upon addition of propene both compounds rearrange into two cycloalkanes wherein the larger ring of the spiroalkane is preserved and substituted with ethylidene and a vinyl group.
Conformational analysis of benzoanellated nine-membered rings, Part 1. 1,4,5,7-tetrahydro-3H-2,6-benzodithionin derivatives
作者:Barbara Rys、Helmut Duddeck、Monika Hiegemann
DOI:10.1016/s0040-4020(01)86418-8
日期:1991.1
The NMR spectra of compounds 1–5, recorded at different temperatures, are discussed and interpreted in terms of conformational equilibrium. Ground state conformations are found to be chiral, ring inversionbarriers are surprisingly high (ca 48 kJ/mol).
dialkylation of alkene is an efficient protocol for constructing useful chemicals, but challenges remain in the unrestricted application of alkylating reagents. Alkyl bromide belongs to the easy-to-access and operable alkyl electrophiles that can be used in reductivecoupling with alkenes. Here, we reported convenient strategies for dialkylcyclization and homodialkylation of unactivated β,γ- and γ,δ-unsaturated