| Part I. Sterically hindered ketones were converted into nitrimines via oximes. The ketones were converted into the oximes by treatment with hydroxylamine hydrochloride in an alcoholic solution to give the corresponding oximes in 24 to 74% yield. The oximes were treated with nitrosyl chloride in pyridine to afford the nitrimines in 39 to 65% yield.; Ammonolysis of the nitrimines under anhydrous conditions afforded the sterically hindered imines in 73 to 100% yield.; When camphor imine (110) and fenchone imine (111) were warmed slightly above room temperature, fragmentation occurred. Camphor imine (110) afforded 2,3,3-trimethyl-4-cyanomethylcyclo- pentene (94), 2-methylene-3,3-dimethyl-4-cyanomethylcyclopentane (95) and camphor (96). Fenchone imine (111) afforded fenchone (98), 2-methyl-4-(2-cyanoisopropyl)cyclopentene (99), 3-(2-propenyl)-1-cyano-1-methylcyclopentane (100), 2-methylene-4- (2-cyano-isopropylcyclopentane (101), and 4-isopropylidene-1-methyl-1-cyanocyclopentane (102).; Attempts to prepare thiocamphor and thiofenchone by treating the corresponding nitrimines with anhydrous sodium sulfide led instead to fragmentation of the nitrimines.; Part II. 1,3-Dithiole-2-one (50) and 4,5-dimethyl-1,3-dithiole-2-one (57) were prepared by ring closure reactions. Potassium-O-isopropyl-dithiocarbonate (53) was treated with bromoacetaldehyde diethyl- acetal (54) to afford O-isopropyldithiocarbonyl acetaldehyde diethyl- acetal (55). Compound 55 was treated with concentrated sulfuric acid at room temperature to afford 1,3-dithiole-2-one (50). The 4,5-dimethyl-1,3-dithiole-2-one (57) was prepared by treating 53 with 3-bromo-2-butanone (58) to afford O-isopropyl-dithiocarbonate-2-butanone (59); 59 was treated with concentrated sulfuric acid to afford 57. When 50 and 57 were treated with a variety of thionating reagents, the corresponding thiones, 1,3-dithiole-2-thione (14) and 4,5-dimethyl-1,3-dithiole-2-thione (59) were obtained.; In order to prepare the thione and selone from a common inter- mediate, diisopropylaminodithiolium salts 70 and 73 were prepared. When 70 and 73 were treated with sodium hydrogen sulfide, the corresponding thiones were not obtained and the starting materials were quantitatively recovered. The unhindered piperidinium salts 77 and 79 were also prepared.; 1,3,4,6-Tetrathiapentalene-2,5-dione (83) was prepared by treat- ment of methyldichloroacetate (84) with 53 to afford methyl 2,2-bis- (O-isopropyldithiocarbonyl)acetate (85). When 85 was treated with concentrated sulfuric acid, 83 was obtained. The mono thione was prepared by treating 83 with phosphorus pentasulfide or with bis- (tricyclohexyltin)sulfide (87) - boron trichloride (88). The mono- selone of 91 was prepared by treating 83 with bis(tricyclohexyltin)- selenide (92).; The coupling reactions of 50, 57, 14, 59, 62 and 63 were studied using triphenylphosphine (117), tri-n-butylphosphine (126) and trimethylphosphite (92). (Abstract shortened with permission of author.)... |
