Ketones, preparation from carboxylic acid 2,2-DIMETHYL

Notable examples of general synthetic procedures in Volume 47 include the synthesis of aromatic aldehydes (from dichloro-methyl methyl ether), aliphatic aldehydes (from alkyl halides and trimethylamine oxide and by oxidation of alcohols using dimethyl sulfoxide, dicyclohexylcarbodiimide, and pyridinum trifluoro-acetate the latter method is particularly useful since the conditions are so mild), carbethoxycycloalkanones (from sodium hydride, diethyl carbonate, and the cycloalkanone), m-dialkylbenzenes (from the />-isomer by isomerization with hydrogen fluoride and boron trifluoride), and the deamination of amines (by conversion to the nitrosoamide and thermolysis to the ester). Other general methods are represented by the synthesis of 1 J-difluoroolefins (from sodium chlorodifluoroacetate, triphenyl phosphine, and an aldehyde or ketone), the nitration of aromatic rings (with ni-tronium tetrafluoroborate), the reductive methylation of aromatic nitro compounds (with formaldehyde and hydrogen), the synthesis of dialkyl ketones (from carboxylic acids and iron powder), and the preparation of 1-substituted cyclopropanols (from the condensation of a 1,3-dichloro-2-propanol derivative and ethyl-... 

Ketones can also be prepared directly from carboxylic acids by activation as mixed anhydrides by dimethyl dicarbonate.236 These conditions were used successfully with alkanoic and alkanedioic acids, was well as aromatic acids. 

The Swem Oxidation of alcohols avoids the use of toxic metals such as chromium, and can be carried out under very mild conditions. This reaction allows the preparation of aldehydes and ketones from primary and secondary alcohols, resp. Aldehydes do not react further to give carboxylic acids. A drawback is the production of the malodorous side product dimethyl sulphide. 

Dilithium tetrachlorocuprate is recommended as an additive for cross coupling of Grignard compounds with tosylates even allylic and benzylic acetates give good yields . a-Methylene-ketones, -carboxylic acids and -lactones have been prepared via sulfides and sulfoxides. A convenient and general synthesis of acetylene derivatives from boranes via the reaction of iodine with lithium 1-alkynyltriorganoborates has been published ar-Nitrostyrenes can be easily obtained by a Wittig synthesis with formaldehyde in an aqueous medium . A new synthesis of unsym. ketones by reaction of dialkyldiloroboranes with lithium aldimines has recently been published . Metallo aldimines have also served for the synthesis of a variety of other compound classes such as a-hydroxyketones, a-keto acids, nitriles, and for the asym. synthesis of a-amino acids . Polycondensations of malononitriles with benzylic chlorides have been carried out quantitatively under mild conditions in dimethyl sulfoxide with triethylamine as acid acceptor . Carbonyl compounds can react with dibromoacetonitrile to yield a-bromo esters with additional carbon atom . ... 

Julia substrate 41 was prepared as follows. Cyclopropylketone 42 was converted to the corresponding /3-ketoester using sodium hydride and dimethyl carbonate. The anion derived from the /3-ketoester was alkylated with allylic bromide 43 to provide 44a. Ester hydrolysis, decarboxylation of the intermediate /3-ketoacid, and esterification of the terminal carboxylic acid using diazomethane, gave ketone 44b (CJH-5). 

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