REDUCTONES OF TETRONIC, THIOTETRONIC AND TETRAMIC ACIDS, .2. REDUCTONES BY RHODIUM-CATALYZED DECOMPOSITION OF DIAZO-COMPOUNDS

The diazoketones 2 have been synthesized by diazo transfer reaction wi th 2-azido-3-ethylbenzthiazolium tetranuoroborate. The rhodium-catalyz ed decomposition of compounds 2 in tert-butyl alcohol at 130 degrees C furnishes the reductone monoethers 3 and after deprotection the aci-r eductones 4. Methylation of compounds 4 with diazomethane proceeds ste pwise leading first to the monoethers 5 and then to the diethers 6. Th e thiolactone 4b and even more the lactams 4c and 4d are stronger redu cing agents than the lactone 4a.