Treatment of 5,5-dimethyl-2-cyclohexen-1-one and isophorone with phosphomolybdic acid, potassium dichromate, cupric sulfate, and air gives 5,5-dimethyl- and 3,5,5-trimethyl-2-cyclohexene-1,4-dione, respectively. In the latter reaction treatment of the crude product with aqueous base leads to the formation of 2,3,6,7-tetrahydro-2,2,6,6,-tetramethylanthracene-1,4,5,8-tetrone.

Synthesis of cyclic 2-enones from cyclic 1,3-diketones

The oxidation of 2-cyclohexen-1-ones to 2-cyclohexene-1,4-diones

Efficient syntheses of insect sex pheromones emitted by the boll weevil and the red bollworm moth

The synthesis of (±)-dihydrofomannosin acetate [5-acetoxymethyl-1-(4,4-dimethyl-2-oxocyclopentyl)-3-oxabicyclo[4.2.0]oct-5-en-4-one] is described. Photocycloaddition of 4-(2-acetoxy-4,4-dimethylcyclopentyl)-2(5H)-furanone to ethylene gave 5-(2-acetoxy-4,4-dimethylcyclopentyl)-3-oxabicyclo[3.2.0]heptan-2-one, which was converted into ethyl [2-acetoxymethyl-2-(2-acetoxy-4,4-dimethylcyclopentyl)cyclobutyl]glyoxylate by the reaction with 2-methylthio-1,3-dithiane, followed by acetylation and ethanolysis. Introduction of an additional one carbon unit to the glyoxylate was accomplished by the Wittig reaction, and the subsequent hydrolysis and lactonization afforded 1-(2-hydroxy-4,4-dimethylcyclopentyl)-5-methylene-3-oxabicyclo[4.2.0]octan-4-one, which was transformed into 5-acetoxymethyl-5-hydroxy-1-[4,4-dimethyl-2-(tetrahydropyranyloxy)cyclopentyl]-3-oxabicyclo[4.2.0]-octan-4-one. Mesylation followed by elimination and oxidation led to (±)-dihydrofomannosin acetate.

Synthesis of (±)-Dihydrofomannosin Acetate

2.02 – Alkyl Chalcogenides: Oxygen-based Functional Groups

The carbon–carbon π-bond plays a central role in synthesis, not only in its own right as a functional group present in many target molecules, but also as a synthetic intermediate through which an extraordinary number of important transformations are accomplished. In fact, nearly two complete volumes of ‘Comprehensive Organic Synthesis’ are devoted to alkene reactions, many of which require stereo- or regio-isomerically homogeneous starting materials if they are to be useful. This chapter examines one of the more important general routes to this fundamentally important functional group, the transformation of ketones into alkenes.

Synthesis of cyclic 2-enones from cyclic 1,3-diketones

Citations

The oxidation of 2-cyclohexen-1-ones to 2-cyclohexene-1,4-diones

Efficient syntheses of insect sex pheromones emitted by the boll weevil and the red bollworm moth

Synthesis of (±)-Dihydrofomannosin Acetate

2.02 – Alkyl Chalcogenides: Oxygen-based Functional Groups

Reduction of Ketones to Alkenes

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