Cyclization process for making oxazolikinones

A process for the synthesis of a compound of general formula II:

• ##STR21## wherein:
• R.sup.2 and R.sup.3 are each independently hydrogen or C.sub.1 -C.sub.4 alkyl;
• A is an aromatic or heteroaromatic ring system optionally substituted with one or more substituents selected from:
• halogen, C.sub.1 -C.sub.10 hydrocarbyl, --S(C.sub.1 -C.sub.10 hydrocarbyl), --SO(C.sub.1 -C.sub.10 hydrocarbyl), --SO.sub.2 (C.sub.1 -C.sub.10 hydrocarbyl), cyano, nitro, SCN, SiR.sup.c.sub.3 where each R.sup.c is independently C.sub.1 -C.sub.4 alkyl or phenyl, COR.sup.7, CR.sup.7 NOR.sup.8, NHOH, ONR.sup.7 R.sup.8, SF.sub.5, COOR.sup.7, SO.sub.2 NR.sup.7 R.sup.8, OR.sup.9 or NR.sup.10 R.sup.11 ;
• and in which any ring nitrogen atom may be quaternised or oxidised;
• alternatively, any two substituents of the group A may combine to form a fused 5- or 6-membered saturated or partially saturated carbocyclic or heterocyclic ring in which any carbon or quaternised nitrogen atom may be substituted with any of the groups mentioned above for A or in which a ring carbon atom may be oxidised;
• R.sup.7 and R.sup.8 are each independently hydrogen or C.sub.1 -C.sub.10 hydrocarbyl;
• R.sup.9 is hydrogen, C.sub.1 -C.sub.10 hydrocarbyl, SO.sub.2 (C.sub.1 -C.sub.10 hydrocarbyl), CHO, CO(C.sub.1 -C.sub.10 hydrocarbyl), COO(C.sub.1 -C.sub.10 hydrocarbyl) or CONR.sup.7 R.sup.8 ;
• R.sup.10 and R.sup.11 are each independently hydrogen, C.sub.1 -C.sub.10 hydrocarbyl, O(C.sub.1 -C.sub.10 hydrocarbyl), SO.sub.2 (C.sub.1 -C.sub.10 hydrocarbyl), CHO, CO(C.sub.1 -C.sub.10 hydrocarbyl), COO(C.sub.1 -C.sub.10 hydrocarbyl) or CONR.sup.7 R.sup.8 ;
• any of the hydrocarbyl groups within the group A may optionally be substituted with halogen, hydroxy, SO.sub.2 NR.sup.a R.sup.b where R.sup.a and R.sup.b are independently hydrogen or C.sub.1 -C.sub.6 alkyl, cyano, nitro, amino, mono- and dialkylamino in which the alkyl groups have from 1 to 6 or more carbon atoms, acylamino, C.sub.1 -C.sub.6 alkoxy, C.sub.1 -C.sub.6 haloalkoxy, C.sub.1 -C.sub.6 alkylthio, C.sub.1 -C.sub.6 alkylsulphinyl, C.sub.1 -C.sub.6 alkylsulphonyl, carboxy, carboxyamide in which the groups attached to the N atom may be hydrogen or lower hydrocarbyl optionally substituted with halogen;
• alkoxy carbonyl wherein the alkoxy group may have from 1 to 6 or more carbon atoms, or aryl;
• the process comprising cyclising a compound of general formula VII:
• ##STR22## wherein A, R.sup.2 and R.sup.3 are as defined for general formula II, R.sup.20 is hydrogen, benzyl or benzyl substituted with up to five substituents selected from halo, C.sub.1 -C.sub.6 alkyl, O(C.sub.1 -C.sub.6 alkyl) or nitro and R.sup.21 is C.sub.1 -C.sub.8 alkyl, benzyl or benzyl substituted with up to five of the substituents mentioned above for R.sup.20.