101403-36-5Relevant articles and documents
Cycloaddition Reactions of Phenylallene. Ring Closure of the Diradical Intermediate Involving the Aromatic Ring
Pasto, Daniel J.,Yang, Shung Hua
, p. 1676 - 1680 (2007/10/02)
Phenylallene (PHA) reacts with 1,1-dichloro-2,2-difluoroethene (1122) to produce, in part, the two benzylidene-containing cycloadducts 5 and 6, with the E isomer 5 predominating as expected.In addition, two stereoisomeric 2:1 PHA-1122 adducts of structure 8 and 9 are formed by reaction of the PHA cyclodimers 10 with 1122.The reaction of PHA with diethyl fumarate (DEF) produces, in part, the two cycloadducts 15 and 16 in which the Z isomer 16 predominates.The major product 19 is formed by ring closure at an ortho position of the aromatic ring in the E diradical intermediate, followed by an ene reaction of the intermediate with DEF.The reaction of PHA with N-phenylmaleimide (NPMI) similarly produces cycloadducts 20 and 21 in which the Z isomer 21 predominates.The major product 23 is formed by ring closure at an ortho position of the aromatic ring followed by hydrogen sigmatropic rearrangement and loss of hydrogen.The dominant formation of the E isomer 5 with 1122 and the Z isomers 16 and 21, and 19 and 23, in the reactions with DEF and NPMI indicate a highly reversible formation of the Z diradical intermediate 27.The cycloaddition of PHA with acrylonitrile produces essentially only a normal distribution of cycloadducts, indicating that cleavage of the Z diradical intermediate does not occur.
