73936-93-3Relevant academic research and scientific papers
Carbene-carbene rearrangements as a route to 1,5-dihydropentalene
Brinker, Udo H.,Fleischhauer, Ilona
, p. 4495 - 4502 (1981)
1,5-Dihydropentalene (4) is formed as the main product on treatment of trans-1,2-bis(2,2-dibromocyclo-propyl)ethene 3 with methyllithium at -40°. In addition the reaction affords 1- and 2-propadienylcyclopentadienes (5a) and (5b), and trans-1,2,4,6,7-octapentaene (6), new CsHs isomers. Diets-Alder adducts of 4,5a and 5b were obtained in the reaction with perfluorobut-2-yne. The formation of 1,5-dihydropentalene 4 is explained by a double ring expansion sequence involving consecutive carbene-carbene rearrangements with 1,3-carbon and subsequent 1,2-hydrogen shifts, supported by the reaction of double labelled (13C-depleted) 3. From readily available 3 at low temperatures formation and fusion of two 5-membered rings are achieved in one step.
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.
CARBENE-CARBENE REARRANGEMENTS AS A ROUTE TO 1,5-DIHYDROPENTALENE
Brinker, Udo H.,Fleischhauer, Ilona
, p. 4495 - 4502 (2007/10/02)
1,5-Dihydropentalene (4) is formed as the main product on treatment of trans-1,2-bis(2,2-dibromocyclopropyl)ethene 3 with methyllithium at -40 deg C.In addition the reaction affords 1- and 2-propadienylcyclopentadienes (5a) and (5b), and trans-1,2,4,6,7-octapentaene (6), new C8H8 isomers.Diels-Alder adducts of 4, 5a and 5b were obtained in the reaction with perfluorobut-2-yne.The formation of 1,5-dihydropentalene 4 is explained by a double ring expansion sequence involving consecutive carbene-carbene rearrangements with 1,3-carbon and subsequent 1,2-hydrogen shifts, supported by the reaction of double labelled ((13)C-depleted) 3.From readily available 3 at low temperatures formation and fusion of two 5-membered rings are achieved in one step.
