Simple and efficient synthesis of bromine-substituted 1,3-dienes and 1,3,5-cycloheptatriene by vacuum pyrolysis of gem-dibromocyclopropanes
2001; Elsevier BV; Volume: 42; Issue: 19 Linguagem: Inglês
10.1016/s0040-4039(01)00460-9
ISSN1873-3581
AutoresNick Henry Werstiuk, Chandra D. Roy,
Tópico(s)Cyclopropane Reaction Mechanisms
ResumoAbstract To establish whether the results obtained by the gas phase pyrolysis of 6,6-dihalobicyclo[3.1.0]hexanes by HeI photoelectron spectroscopy using a high power CW CO2 laser as a directed heat source can be achieved on a preparatory scale using a modified apparatus, we carried out the gas phase pyrolysis of a few representative gem-dibromocyclopropanes such as 1,1-dibromo-2,2,3,3-tetramethylcyclopropane ( 1 ), 1,1-dibromo-2,2-dimethyl-cyclopropane ( 2 ), 1,1-dibromo-cis-2,3-dimethylcyclopropane ( 3 ), 1,1-dibromo-trans-2,3-dimethylcyclopropane ( 4 ), 6,6-dibromobicyclo[3.1.0]hexane ( 5 ) and 7,7-dibromobicyclo[4.1.0]heptane ( 6 ). Except 7,7-dibromobicyclo[4.1.0]heptane, that gave 1,3,5-cycloheptatriene in 72% yield at 525°C, 1 , 2 , 3 , 4 and 5 readily lose HBr at 400–560°C in the gas phase to produce β-bromo-1,3-dienes in high chemical yields and purity. The dienes are potentially useful starting substrates for the Diels–Alder reactions.
Referência(s)