Iied~~cti\.e cleavage of the ozonides of aliphatic acids and their esters by sodiuru boroh3-clridc or by hydrogenation produces w-hydroxy aliphatic acids and w-hydrosy aliphatic esters, respectively, in high yields. INTRODUCTIOSw-Difunctional aliphatic compounds have found 1nuc11 ernplo>-~nent in the synthesis of higher aliphatic compounds. Among these, substances having two different terminal functions are the most favored, and probably the most important reagents for chai~l extension are the esters of the w-halogeno acids. These compounds, in various chainlengths, were required for condensation with ~nalonic ester derivatives in the preparation of branched alkanedioic acids (1, 2, 3, 4) in this laboratory. With the exception of those members of the series of very short chain-length, only one w-bromo acid, ll-bromoundecanoic, is easil), available and this substance is best prepared by the peroxiclecatal>,zed addition of hydrogen bromide to 10-unclecenoic acid ( 5 ) . The latter compound is unique among the terminal unsaturated acids in that it is available in quantity ancl this method of preparation cannot be regarded as a neth hod of general applicability. Use of the more common unsaturated acids with non-terminal olefinic linkages as starting materials for the preparation of w-hydroxy acids and w-bromo acids was first explored b>-Adams ( G , 7), who ozonized the esters and isolated w-aldehydo esters. These compounds were then reduced to give the esters of the w-hydroxy acids. A practical difficulty in preparations of this type is the inevitable oxidation of a portion of the aldehydo ester to the half ester of the corresponding dicarboxylic acid. contamination of intermediates with substances in the dicarboxylic acid series is undesirable as such compounds are usually high nlelting and insoluble and therefore difficult to remove. I t is desirable, therefore, to obviate the sensitive aldehyde intermediate by exploitation of the new metal hydride reagents (8) and by selective reductive cleavage of the ozonide-ester prepare the hydrosy ester without isolatioil of the aldehyde. A similar observation on the preparation of primary alcohols by the borohydride cleavage of ozonides appeared while this work mas in progress (9).We have compared the high-pressure 11)-drogenolysis of certain ozonides with their reductive cleavage by sodium borohydricle and the results are su~n~narized in Table I.Yields of hydroxy ester were found to be superior lvllen the borohydride was usecl and the products were also of higher purity as indicated by a narrow boiling range and ease of crystallizatioil of the phenylurethane. When the scale of the preparation was increased, the yield by borohydride cleavage remained the same but the yield b y high-pressure hydrogenation diminished. Sodium borohydride is still an expensive reagent and it may therefore be more ecoilomical to use the hydrogenation method on a large scale.
Oximes and semicarbarones are oxidized by ceric ammonium nitrate to the parent carbonyl cornpound in good yield. Suitable solvent systcms includc aqucous alcohols, acetonitrile, and acetic acid. The reaction is rapid at 0" or below. This procedure for regeneration of aldehydes and ketones from these derivatives may be preferable to the well-known hydrolytic procedures in some cases. The stoichiometry of the reaction was studied by isothermal calorimetry; two equivalents of oxidant are consumed by one mole of oxime evolving approximately 40 kcal/mole. A smaller consunlption of oxidant by hexane-2,s-dione dioxinie was attributed to stabilization of the monoxime as a nitroso chelate. Gaseous products were studied by infrared spectroscopy and nitrous oxide was identified as the sole product absorbing between 3 and 15 p. A reaction mechanism is proposed involving one-electron oxidation to the iminoxy radical, oxidized by a second one-electron step to the cc-hydroxy nitroso compound. Dimerization and elimination of hyponitrous acid gives the carbonyl compound. Nitrocyclohexane was absent from the oxidation product from cycIohexanone oxime. Carvone oxime was oxidized to carvone without racemiration or significant attack of the olefin groups.
Extension of an aliphatic chain by five, six, or seven carbon atoms Inay be achieved by adding to it a 5-, 6-, or 7-membered olefinic alicycle and subsequently breaking the double bond. .Addition of the ring is achieved by a Grignard reaction between an all;ylrnagnesi~~m bromide and a cyclic ketone, and the resulting 1-alkylcycloolefin is opened by ozonolysis. The end product is a 5-, 6-, or 7-keto acid.
1-Decene ozonide (1) was isolated by column chromatography of the mixed products of ozonation of 1-decene (2) in several nonpolar solvents. 1-Methoxy- (3) and 1-tertiary butoxynonane-1-hydroperoxide (4) were similarly obtained. The thin-layer chromatographic separation of these products from each other and from other ozonation products was examined. Compounds 3 and 4 were smoothly oxidized to di-(1-alkoxyalkyl)peroxides by Ce(IV). The stoichiometry of this reaction, examined by isothermal calorimetry, was 1:1. Compounds 1,3, and 4 were oxidized by CF3CO3H and by other oxidizing agents to nonanoic acid with chain degradation loss of 2–30%.
Chromyl chloride in carbon tetrachloride solution reacts in the cold with cyclohexene, cyclopentene, and 1-hexene to give the various isomeric chlorohydrins as the major products. The major product from 2-methyl-1-pentene was 2-methylpentanal. Significant amounts of α-chloro carbonyl compounds and some α,β-unsaturated carbonyl compounds were also produced. The significance of these results is discussed.
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