Solvent-Free Rearrangement under Photoirradiation

Type of reaction rearrangement Reaction condition solid-state 

Keywords 1,4-pentadiene derivatives, 2-cyclohexenone derivatives, di-7r-methane rearrangement, photoirradiation 

A crystalline film of 314 mg (0.744 mmol) of l,l,3,3-tetraphenyl-5,5-dicyano-1,4-pentadiene 1 a, deposited by slow evaporation of a 20% ether in hexane solution, was irradiated at 78 °C for 2.5 h through Pyrex. The resulting orange-red solid was subjected to preparative HPLC eluted with 8% ether and 0.5% acetonitrile in hexane to give 227.1 mg (72.3%) of starting diene and 74.8 mg (23.8%) of 2 a as a pale purple-red solid. Recrystallization from ether-hexane yielded 69.7 mg (21.6%) of 2a as a white solid (mp 125-128°C). 

Keywords benzyl phenyl sufone, /1-cyclodcxtrin, photorearrangement, 2-methyl-phenyl phenyl sulfone 

2-dialkyIbenzimidazoline 1 was heated to 200 °C in a sealed tube and the rearranged product 2 was isolated by column chromotography with petroleum ether. 

References C.M. Reddy, P. L. Prasunamba, P. S.N. Reddy, Tetrahedron Lett., 37, 3355 

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