Studies on the Synthesis of Heterocyclic Compounds 775. Synthesis of b-Lactams by Acid Chloride- and Phosphate Anhydrideimine Methods

Several 1,3,4-substituted 2-azetidinones (12 % 2 5 1 were s~nthesised by the acid chloride-and phosphate anhydrideimine methods.There are various methods developed for the synthesis of 0-lactams.2 r 3 Among them, the acid chloride-imine method introduced by Bose and c o -~o r k e r s ~~~ is one of the most general method for preparation of 6-lactams.Recently they further found an alternative method using phosphorylating agents, in which the phosphate anhydride intermediate 15) was po~tulated.~We have synthesised several 8-lactams by both methods and here wish to report these results. Scheme 1 (A) Acid chloride-Imlne MethodComercially available carboxylic acids (1 ?. 4) were firstly converted into the corresponding acid chlorides (A) with thionyl chloride or oxalyl chloride as usual.Diphenylacetyl chloride was treated with triethylamine according to Bachi's procedurelo to give the ketenell, which was added to a solution of y-benzylideneglycinates (7 s 9 ) in dry benzene.The reaction was carried out overnight at room temperature.In the case of the other acid chlorides from the carboxylic acids ( 2 ?. 4 ) . the acid chlorldesweredirectly addedtoa mixtureof theimines (7 z 11)and triethylamine in dry methylene chloride and the resulting mixture was stirred for 1 h at room temperature.The results are sumarised in Tables 1 and2.(B)