THE FORMATION OF PYRAZINES FROM N-β-KETO IMINOTRIPHENYLPHOSPHORANES; IMINOPHOSPHORANE-MEDIATED SYNTHESES OF 2,2,4,4-TETRAPHENYL-N,N′ -BIS(2-PENTANE-3-ON)- CYCLOBUTANE-1,3-DIIMINE; 1,3,4-OXADIAZOLES; 2-AMINO-3,5-DIHYDROIMIDAZOL-4-ONES; AND 2- DIPHENYLMETHYL-I,5-DIHYDROIMIDAZOL-4-ONE

Abstract

The aza-Wittig reaction has been applied to the synthesis of the unstable N-β-keto ketenimine (18), which dimerize spontaneously, forming the very sterically hindered 2,2,4,4-tetraphenyl-N,N′-bis (2pentane-3-on)-cyclobutane-1,3-diimine (21). Iminophosphoranes (33) and (38) are used for the preparation of some novel 1,5 and 3,5-dihydroimidazol-4-ones (36), (41a-b), (42). N-acylamino iminotriphenylphosphoranes (2a-d) are applied for the syntheses of a series of 1,3,4-oxadiazoles (32). The mechanism of the decomposition of the unstable N-β-keto iminotriphenylphosphoranes (1) into pyrazines and triphenylphosphine oxide has been investigated.

Key Words:

• Iminophosphoranes
• β-keto carbodiimides
• N-,β-keto ketenimines
• heterocycles.