?-Substituted phosphonates. 64. Phosphono-Substituted Imidazoles and other heterocycles from diethyl [(2,2-dichloro-1-isocyano)-ethenyl]phosphonate
作者:Michael Schnell、Matthias Ramm、Angela K�ckritz
DOI:10.1002/prac.19943360107
日期:——
The reaction of diethyl [(1-isocyano-2,2-dichloro)-ethenyl]phosphonate (1) with mono- and bifunctional aliphatic and aromatic amines and thiols has been studied. Because 1 is a push-pull olefine, a nucleophilic attack can take place at the halide-substituted carbon atom. On the other hand, 1 possesses with the isocyano group a further reactive centre, which is able to undergo typical isocyanide reactions. With secondary and ethylene-bridged bifunctional nucleophiles the substitution of the chloro atoms of 1 furnishes ketene N,N-, N,S- and S,S-acetals (8, 12, 14). By treating 1 with primary amines imidazoles 6 are obtained, an alpha-addition of an amino function to an isocyano group under mild conditions being involved. The isocyano-substituted cyclic ketene N,N-acetal 12 a inserts acceptor-substituted isocyanides forming the fused pyrazines 18. The structure of 18 a is corroborated by X-ray crystal structure analysis.