100515-96-6Relevant articles and documents
Carbene Rearrangements, XX. trans-2-(1,3-Butadienyl)cyclopropylidene: Generation and Reactive Behavior
Brinker, Udo H.,Fleischhauer, Ilona
, p. 1244 - 1268 (2007/10/02)
1- and 2-Vinyl-1,3-cyclopentadiene (19 and 20) and trans-1,2,4,6-heptatetraene (21) are formed from trans-2-(1,3-butadienyl)cyclopropylidene(oid) (18), which is generated from the dibromocarbene adduct 17 with methyllithium at 0 deg C.The mechanisms of the rearrangements of 18 have been examined by 12C-labeling (12C >/= 99.95percent) in 17. 21 is formed from 18 by rupture of the distal bond B of the cyclopropylidene.Breakage of the lateral bond A in 18 induces a carbene-carbene rearrangement with 1,3-C migration.The rearranged carbene 28 stabilizes itself by three routes.The product ratio of the competing reactions in 18 is temperature dependent.At lower temperatures the carbene-carbene rearrangement 18 -> 20 predominates, at higher temperatures increased formation of 21 takes place. - If 18 is generated by pyrolysis of the organotin compound 34, the high temperature (260 deg C) necessary for the decomposition favors the allene formation and suppresses the carbene-carbene rearrangement. - 21 is also formed when 18 is released from the N-nitrosourea 36b. 19 and 20 decompose under the reaction conditions. - A new method for the generation of carben(oid)s is described.