2-Azetidiniminium salts synthesis

Ab initio calculations indicate that in the gas phase the reaction of ketene inline and formaldehyde is concerted but asynchronous whereas in dichloromethane it is a two-step zwitterionic reaction.38 The 2 + 2-cycloadditions of keteniminium triflates with imines yields 2-azetidiniminium salts with cis stereoselectivity.39 The intramolecular 2 + 2-cycloaddition of ketenimines with imines (24) provides a novel synthesis of azeto[2,l-Z>]quinazolines (25) (Scheme 9).40... 

For reviews on the synthesis of p-lactams, see a) Sheehan JC, Corey EJ (1957) Org Reac 9 Chapt 6 b) Mukerjee AK, Srivastava, RC Synthesis 1973 373 b) Isaacs NS (1976) Chem Soc Rev 76 181 c) Bose AK, Manhas MS (1976) Lect Heterocycl Chem 3 43 d) Mukerjee AK, Singh AK (1978) Tetrahedron 34 1731 e) Koppel GA (1983) In Hassner A (ed) Small ring heterocycles-azetidines, p-lactams, diazetidines and diaziridines, Wiley, New York, Chapt 2 f) From azetidiniminium salts, see Ghosez L, Bogdan S, Ceresiat M, Frydrych C, Brynaert J, Portuguez MM, Huber I (1987) Pure Appl Chem 59 393... 

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