Thianaphthenequinone, reaction with

If the carbonyl grou]) in the 3-position of N-methylisatin or tlii-ana])hthencquinone is blocked by formation of an oxime (cf. 112), A -methylation of the oxime group occurs instead of ring expansion on reaction with diazomethane. In methanol, thianaphthenequinone oxime iV-mcthyl ether (113) then undergoes ring opening catalyzed by diazoniethane (113 114). 

Naphtho[2,l-6]furo[2,3-c][l,2,4]triazines 198 were prepared (88JHC-1117) by the reaction of 4-5-benzocoumaran-2,3-dione with thiosemicar-bazide to give 195, whose ethylation in the presence of sodium hydroxide gave 197 via 196. Reaction of 197 with aniline gave 198 via the first displacement of the ethylthio group whose product could be isolated with a shorter reaction time. On the other hand, the similar sequence of reactions on coumaran-2,3-diones differs markedly from that of 4,5-benzocoumaran-2,3-diones, where the cyclization of 195 to 198 could not be effected. The behavior of the later dione resembles that of isatin and thianaphthenequinone (Scheme 41). 

Thianaphthenequinone (109) and diazomethane give a different reaction from that found with isatin, A -raethylisatin and coumarandione. In as far as crystalline products could be isolated, the ring expansion occurs here between the sulfur and the carbonyl group in the 2-position. Depending on the solvent, there are formed 3-hydroxy-thiochromone (110), its 0-methyl derivative (111), or (presumably by attack on the 3-keto group of the tautomeric 3,4-diketo form of 110), 3,3 -epoxy-3-methylthiochromone (108). 

---