R. Cassis

Studies on Quinones. XI. Synthesis of Quinones from Hydroquinones by Using Manganese Dioxide and Acid-Impregnated Manganese Dioxide1

Abstract The preparation of a variety of quinones by oxidation of hydroquinones with manganese dioxide and manganese dioxide impregnated with nitric acid, in methylene chloride solution, is described.

Studies on Quinones XVII1. The Reaction of Acylbenzo-Quinones with Hydrazoic Acid: A Route to the Preparation of 2,1-Benzisoxazol-4,7-Quinones

Abstract A straightforward route to 2,1-benzisoxazol-4,7-quino-nes by oxidation of acylazido hydroquinones, obtained through reaction of acylbenzoquinones with hydrazoic acid, is described.

Studies on quinones. XV. A convenient entry into thetetrahydrophenanthrene-1,4-quinone system utilizing the dienone-phenol rearrangement of spiro [cyclopentanenaphthalene]triones

Abstract A four-step approach to the synthesis of 10-acetyloxi-5,6,7,8-tetrahydrophenanthrene-1,4-derivatives, starting from acylbenzoquinones, is described.

Dienone-phenol rearrangement of naphthalenetriones. A route to 10-acetoxy5,6,7,8-tetra hydrophenanthrene-1,4-diones

Naphthalene-1,4,5(8H)-triones (17) and (18) prepared in a three-step approach from the corresponding acylbenzoquinones (1) and (2), undergo an unusually rapid dienone-phenol rearrangement in acetic anhydride–sulphuric acid solution to give 5-acetoxy-7,8-dimethyl- and 5-acetoxy-6,7,8-trimethyl-1,4-naphthoquinone (19) and (20) in good yields.Starting from the acylbenzoquinones (1), (2), and (3) the spironaphthalenetriones, (30), (31), and (32) were synthesized through the following sequence: (a) addition of enamine (6) to acylquinones, (b) acid-catalysed rearrangement of the spirobenzofurans (23), (24), and (25), and (c) oxidation, with silver carbonate–Celite reagent, of spironaphthalenones (27), (28), and (29) generated in the latter step. Quinones (30), (31), and (32) were subjected to dienone-phenol rearrangement to produce the corresponding angular tricyclic quinones (33), (34), and (35) in high yields.The dihydroxyspironaphthalenone (27) afforded the substituted phenanthrene (36) under diendnephenol rearrangement conditions. However, the structurally related naphthalenones (13) and (14) are unreactive to this isomerisation.