n heterocyclic reagents 2 and 3 are known and commercially available or may be prepared according to known procedures see for example advances in heterocyclic chemistry pp 1 56 vol 3 1964 and pp 71 121 vol 22 1978 academic press the following list representatively illustrates such reagents str17 wherein all symbols have previously been defined the dotted line indicates both saturated and unsaturated rings relative to the above listed reagents the preferred values for the radical r which is directly attached to the ring nitrogen atom are hydrogen loweralkyl having from 1 10 carbon atoms substituted alkyl wherein the substituent is chloro fluoro hydroxyl alkoxyl substituted alkoxy carboxyl amino sulfo and mono and dialkylamino wherein each aklyl has 1 6 carbon atoms phenylalkyl alkyl moiety having 1 6 carbon atoms and substituted phenylalkyl wherein the substituents are selected from chloro fluoro carboxyl amino hydroxyl lower alkoxyl having from 1 6 carbon atoms sulfo str18 r u00b0 is hydrogen or alkyl having 1 6 carbon atoms the quinolizinium and indolizinium examples are a special category of preferred values of r in that r is there an integral part of a bicyclic system r 39 defined above the preferred values for the other non position specific ring substituent r are chloro fluoro carboxyl and loweralkyl having from 1 6 carbon atoms substituted.