Process for the preparation of 3-substituted-2-azetidinones

A process for the preparation of compounds of the formula ##STR33## which comprises the step of subjecting a compound of the formula ##STR34## to a salt whose anion is a nucleophilic base whose conjugate acid has a pKa in the range of between about -7 to about 14;

• wherein
• R.sub.1 is said nucleophile;
• R is hydrogen,
• R.sub.2 is hydrogen or C.sub.1 -C.sub.6 alkyl;
• R.sub.3 is a leaving group selected from --OSO.sub.n O, where n is 1 or 2 and O is C.sub.1 -C.sub.6 alkyl, C.sub.1 -C.sub.6 substituted alkyl, phenyl or phenyl substituted with 1, 2, or 3 substituents selected from C.sub.1 -C.sub.6 alkyl, C.sub.1 -C.sub.6 alkoxy, C.sub.1 -C.sub.6 alkylthio, nitro, halo, carboxy and amido;
• OPO(phenyl or substituted phenyl).sub.2 ;
• --OPO(C.sub.1 -C.sub.6 alkyl or substituted alkyl).sub.2 ;
• --OPO(OO).sub.2 ;
• O.sub.2 NO;
• or a group of the formula ##STR35## and R.sub.4 is hydrogen, C.sub.1 -C.sub.6 alkyl, or a group of the formula
• --CH.sub.2 CH.sub.2 --R.sub.6
• wherein
• R.sub.6 is 2-furyl, naphthyl, phenyl, phenyl substituted with 1, 2 or 3 substituents selected from C.sub.1 -C.sub.6 alkyl, C.sub.1 -C.sub.6 alkoxy, c.sub.1 -C.sub.6 alkylthio, nitro, halo, carboxy and amido;
• or
• R.sub.6 is a group of the formula
• --COOR.sub.7
• or
• --COSR.sub.7
• in which
• R.sub.7 is selected from C.sub.1 -C.sub.6 alkyl, C.sub.2 -C.sub.6 alkenyl, benzyl, phenyl, or benzyl or phenyl substituted with 1, 2 or 3 substituents selected from C.sub.1 -C.sub.6 alkyl, C.sub.1 -C.sub.6 alkoxy, C.sub.1 -C.sub.6 alkylthio, nitro, halo, carboxy and amido;
• or
• R.sub.4 is a group of the formula ##STR36## wherein L is --OR.sub.7 where R.sub.7 is as defined;
• or
• R.sub.4 is a group of the formula ##STR37## wherein:
• G is trimethylsilylmethyl, hydrogen, C.sub.1 -C.sub.6 alkyl, C.sub.1 -C.sub.6 substituted alkyl, phenyl, or phenyl substituted with 1, 2 or 3 substituents selected from C.sub.1 -C.sub.6 alkyl, C.sub.1 -C.sub.6 alkoxy, C.sub.1 -C.sub.6 alkylthio, nitro, halo, carboxy and amido.