STUDIES ON QUINAZOLINES - VII - REACTIONS OF ANTHRANILAMIDE WITH BETA-DIKETONES - NEW APPROACHES TOWARD THE SYNTHESIS OF TETRAHYDROPYRIDO[2,1-B]QUINAZOLIN-11-ONE DERIVATIVES

Condensation of anthranilamide and its derivatives with various 1,3-cy clohexanediones 5a, b or 2,4-pentanediones under acidic conditions pro duced a variety of heterocycles, leading: to the synthesis of tetrahyd ropyrido[2, 1-6]-quinazolin-11-one derivatives. Condensation of anthra nilamide with 5a or 5b, in the presence of p-toluenesulfonic acid at t he reflux temperature of tetrahydrofuran (THF) afforded compound 6a (4 0%) and compound 7a (22%) or compound 6b (47%) and compound 7b, (39%), respectively. However, reflux of anthranilamide,vith 5a or 5b in 6% e thanolic hydrogen chloride provided compounds 6a and 6b in 77% and 73% yields, respectively. Heating 7a,vith 5a in 6% ethanolic hydrogen chl oride furnished 6a in 82.4% yield. Reaction of anthranilamide with 5c under the same conditions resulted in the formation of 11 (57%), Treat ment of compounds 6a and 6b with NaBH4 furnished 8a,b (89, 87% yields) , which were subsequently subjected to the hlitsunobu reaction to prod uce ahydro-9-methyl-11H-pyrido[2,1-b]quinazolin-11-one (9a) and 6,7,8, 9-tetrahydro-7,7,9-trimethyl-11H-pyrido[2, 1-b]quinazolin-11-one (9b) in 56 and 72% yields, respectively. However, heating 14 with 15a in CH 3CN in the presence of p-toluenesulfonic acid furnished 19 in 31% yiel d, Under similar conditions, treatment of 21,vith 15a provided 23a (42 .4% yield), a key intermediate for the synthesis of rutaecarpine, Anal ogous reaction of 21 with 15b, 15c and 5a provided 22b-d in 63-99.3% y ield, respectively.