Abstract: A process for the synthesis of a compound of general formula II: ##STR1## 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 as defined herein; 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 defined herein for A or in which a ring carbon atom may be oxidised;the process comprising cyclising a compound of general formula VII: ##STR2## 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.sub.21 is C.sub.1 -C.sub.