Thermolysis of 1-(1-Aryl-1-bromomethyl)cyclopropyl Bromides:  A Reinvestigation

Abstract

Two compounds, the (Z)- and (E)-isomers of 2,4-dibromo-1-p-tolyl-1-butene 2a and 3a, respectively, were isolated in 65% total yield when 1-(1-bromo-1-p-tolylmethyl)cyclopropyl bromide (1a) was heated at 150 degrees C for 1 h. 1,1-Dibromo-2-p-tolylcyclobutane (4a), previously reported to be the only product in this reaction, was not detected. The phenyl analogue of 1a reacted similarly and gave the (Z)- and (E)-isomers of 2,4-dibromo-1-phenyl-1-butene 2b and 3b, respectively, in 60% yield. A rationale for the reaction is presented.

A Novel Route to Geminal Dibromocyclobutanes: Syntheses of 2-Substituted Cyclobutanone Acetals and Their Reaction with Boron Tribromide

“…No general synthesis of 2-substituted geminal dibromocyclobutanes has been reported so far. A reinvestigation of the proposed ring enlargement of 1-(1-bromo-1- p -tolylmethyl)cyclopropyl bromide to 1,1-dibromo-2- p -tolylcyclobutane led only to ring opening to give the ( Z )- and ( E )-isomers of 2,4-dibromo-1- p -tolyl-1-butene . This was also the case when at C-1 a phenyl group was present instead of a p -tolyl group …”

New Mixed-Ligand Metal-Containing Monomer Based on Cobalt Acrylate and 4-Phenyl-2,2':6',2″-Terpyridine Ligand: Synthesis, Characteristics and Thermal Properties

“…The first stage of decomposition proceeds up to 150 °C and is associated with the solvent removal. In accordance with the mass spectrum data (m/e 44 and m/e 28), the second stage of decomposition is accompanied by decarboxylation of the mixed-ligand complex with parallel solid-phase polymerization of acrylic fragments, as evidenced by the exothermic effect (116.8 kJ /g) in the range from 280°C to 310°C Based on the results of mass spectra of gaseous products, it can be argued that thermal polymerization is initiated by the Borodin-Hunsdiecker mechanism: the initial light decarboxylation leads to the formation of carbide radicals, which, in turn, causes polymerization and the formation of further polymer [24]. The third stage of decomposition demonstrates a deeper decomposition of the complex.…”

Benzylidenecyclopropane

“…22 Diquinene reacts with benzylidenecyclopropane in the presence of (Cp)Pd(allyl)/P(iPr) 3 (1:1) as catalyst to give the cisoid triquinane in moderate isolated yield (eq 13). 23 Ph + (dba) 2 1,3-Dipolar cycloadditions of benzylidenecyclopropane are scarce and employ the methylenecyclopropane (MCP) unit as a two-carbon component. Benzylidenecyclopropane reacts with phthalhydrazide in the presence of iodobenzene diacetate to form the corresponding dihydrooxazole derivative (eq 14).…”

“…31 The iodohydroxylation of benzylidenecyclopropane with 2.0 equiv of iodine in aqueous acetone affords (1-iodocyclopropyl)(phenyl)methanol, but (1iodocyclopropyl)(phenyl)methanone is obtained as the product when using 5.0 equiv of iodine (eq 19). 16 Ph + 60 ºC 79% The reaction of benzylidenecyclopropane with diethyl ketomalonate provides a facile route to syn-7-hydroxy-5-oxaspiro [2,4]heptan-6-one in the presence of water catalyzed by Sc(OTf) 3 (eq 21). 33 Ph + …”