Ranitidine prodn. by alkylating 2-thiomethyl-furan cpd

Prodn. of furan deriv. Q-SCH2CH2NHC(NHMe)=CHNO2 (I) comprises alkylating the thiol Q-SH (II) with R1R2N-C(-NHMe)=CHNO2 5-(dimethylaminomethyl)-2-furfuryl. R1 is CH2CH2L and R2 is H, or R1R2N is ethyleneimino. L is an eliminable gp. esp. halogen). Cpds. (II) and Q-SC(-NH2)=NH (IV) and their acid addn. salts and (VIII) are new. Pref. (II) is made by reacting Q.OH with thiourea in the presence of conc. HCl to form (IV), which is then hydrolysed with base, esp. in presence of an antioxidant. The resulting free base is esp. converted to its oxalic acid salt. When R1 is CH2CH2L, alkylation is e.g. in aq. THF in presence of base at 10-80 deg.C; or a two-phase system (water-chloroform) is used with a phase-transfer catalyst and base. Where (VIII) is the alkylation agent, reaction is in water, alcohol, etc. or without a solvent at about 100 deg.C. (VIII) is made by reaction of aziridine with L'' alkoxy or alkylthio, esp. methylthio). (I) is a known selective inhibitor of the H2-receptors (GB 1565966).