20968-70-1Relevant articles and documents
Synthesis of Carbo- and Heterocyclic Cyclopropindenes via Cycloaddition of Dienes to Cyclopropenes
Mueller, Paul,Miao, Zhongshan
, p. 1826 - 1836 (1994)
The heterocyclic cyclopropindene 19 was synthesized via cycloaddition of diene 10 to the cyclopropene 11a and subsequent base-induced aromatization.While 19 is isolable, although very short-lived, the oxa analogue 18 decomposed under the conditions required for its preparation.The difluoro derivatives 14 and 15, in which the heterocyclic moiety is saturated, are accessible by the cycloaddition approach, but the corresponding dichlorides are again not isolable.Cyclopropindenes carrying substituents at C(4) have been obtained via cycloaddition of 22b to 1-bromo-2-chlorocyclopropene.The key step of the sequence is a double Curtius degradation of the cycloadduct 23b to the ketone 27a.While aromatization of the alcohol 27b provided the cyclopropindenol 28b, the reaction failed with 27a.Attempts to convert 28b to 1,3-dihydrocyclopropindene (25) via the methanesulfonate 28d failed.
Synthesis of Methyl 3,5,9,11,13-Pentaoxotetradecanoate, a "Skipped" Heptaketide, via Ozonolysis of a Hydroaromatic System
Kirkemo, Curtis L.,White, James D.
, p. 1316 - 1319 (1985)
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Enantioselective formal synthesis of tridemethylisovelleral
R?me, Daniel,Johansson, Martin,Sterner, Olov
, p. 635 - 638 (2007/10/03)
A simple and efficient synthetic route to the bicyclic α,β-unsaturated β-keto ester methyl (3aS,7aS)-6-oxo-2,3,3a,6,7,7a-hexahydro-1H-indene-5-carboxylate, a versatile intermediate in the synthesis of biologically active unsaturated 1,4-dialdehydes, is described. The synthesis includes a chirality introducing nonenzymatic asymmetric desymmetrization (ADS) reaction of a cyclic meso-anhydride 4 and a modified Hofmann method for preparing exocyclic dienes. The ester was synthesized in a moderate overall yield (19%) from 6 and with an excellent enantioselectivity (>90%).
Evidence for 2-Hexene-1,6-diyl Diradicals Accompanying the Concerted Diels-Alder Cycloaddition of Acrylonitrile with Nonpolar 1,3-Dienes
Li, Yufei,Padias, Anne Buyle,Hall, H. K.
, p. 7049 - 7058 (2007/10/02)
The spontaneous reactions of a series of alkyl 1,3-dienes with acrylonitrile (AN) were investigated.Reproducible spontaneous copolymerizations were shown to compete with the expected concerted cycloadditions.For dienes which exist in s-cis/s-trans equilibrium, both copolymer and cycloadduct are formed.Kinetic measurements show that the alternating copolymerization and cycloaddition are two independent paralell second order reactions.With 1,3-cyclohexadiene and 1,2-dimethylenecyclohexane, for which s-gauche is in equilibrium with s-cis, copolymerization still competes with cycloaddition.The s-trans-locked verbenene forms only copolymer, while s-cis-locked cyclopentadiene and 1,2-dimethylenecyclopentane form only cycloadduct rapidly.Our explanation involves a 2-hexene-1,6-diradical, formed by combination between the terminal carbons of the s-gauche or s-trans diene and acrylonitrile.This does not cyclize but initiates copolymerization.Competitively s-cis conformer undergoes classical concerted addition.
