title: An aza cyclopropylcarbinyl-homoallyl radical rearrangement-radical cyclization cascade. Synthesis of dibenzoimidazoazepine and oxazepine derivatives.
abstract: The cycloaddition of the dibenzoxazepinium W-ylides, generated by heating of trans-1-aryl-7,11b-dihydro-1H-azirino[1,2-a]dibenzo[c,f]azepines, to the C═N double bond of 3-aryl-2H-azirines proceeds endo-stereoselectively giving regioisomeric cycloadducts in ca. 1:1 ratio, in good overall yields. In contrast to the dibenzoxazepinium ylides, the cycloaddition of the dibenzazepinium W-ylide proceeds regioselectively but without exo-endo-stereoselectivity. The reasons for this selectivity of the cycloaddition theoretically were studied at the DFT B3LYP/6-31G(d) level. Heating adducts, (2aRS,13SR,13aRS)-13,13a-diaryl-13,13a-dihydro-1H,2aH-azireno[1',2':3,4]imidazo[1,2-d]dibenzo[b,f][1,4]oxazepines and (2aRS,13SR,13aRS)-13,13a- diphenyl-2a,7,13,13a-tetrahydro-1H-azireno[1',2':3,4]imidazo[1,2-a]dibenzo[c,f]azepine, with an excess of AIBN in toluene gave new polyheterocyclic systems via a novel aza cyclopropylcarbinyl-homoallyl radical rearrangement-radical cyclization cascade. The energy profile of the cascade was studied at the DFT UB3LYP/6-31G(d) level. The transient imidazolinylmethyl radical was trapped by the use of other radical initiators as the corresponding peroxide or alcohol.
authors: Department of Chemistry, Saint-Petersburg State University, Universitetskii pr. 26, 198504 St. Petersburg, Russia. alexander.khlebnikov@pobox.spbu.ru
authors: Alexander F
authors: AF
authors: Khlebnikov
authors: Mikhail S
authors: MS
authors: Novikov
authors: Petr P
authors: PP
authors: Petrovskii
authors: Helen
authors: H
authors: Stoeckli-Evans