Photochemical Bergman Cyclization and Related Reactions

Abstract

The titled compounds were prepared by interaction of ethyl 2- (benzo[d]thazol-2-yl)acetate (3) with different arylidinemalononitrile derivatives (4a-c) in EtOH/TEA solution at room temperature. When 3 was treated with 2-(ethoxymethylene)-malononitrile (4f) under same reaction conditions, the ethyl iminothiazolopyridine-4-carboxylate (6) was obtained. Ethyl (amino(methoxy)methyl)-3-(substitutedphenyl)-1-oxo-1H-benzo[4,5]thiazole[3,2-a]pyridine-4carboxylate (8a,b) was obtained from reaction of 3 with different cyanoacrylate derivatives (7a,b) in MeOH/TEA at room temperature, while the diethyl thiazolo[3,2-a]pyridine-4-carboxylate derivative (8c) was obtained under same reaction conditions. The amino-imino derivative (10) was also prepared and used to synthesis new pyrido [3,2e][1,2,4]triaziolo [1,5-c]pyrimidine-5-carboxylate derivatives (12). The structures of all the newly synthesized compounds were confirmed based on their elemental analysis and spectroscopic data.

(Hetero)aromatics from dienynes, enediynes and enyne–allenes

“…68 In a related example, a photo-Hopf cyclization was used for the construction of the naphthalene core upon photocyclization/ aromatizing fragmentation of benzannelated dienynes. 69 The chance of performing Bergman cyclizations by having recourse to a photochemical approach has been sparsely investigated, [70][71][72][73] with particular attention to the biological application of photoactivatable enediynes. 49,74 The approach was particularly efficient with strained ortho-dialkynylarenes (e.g.…”