Bromo methyl ketones from

Treatment of the epoxy sulfones obtained thus with MgBr2 produces a-bromo ketones or a-bromo al-dehyde. This conversion can be applied to stereoselective preparations of a-bromo methyl ketones from cyclohexanone derivatives. Thus, treatment of 17-P-hydroxy-5-a-androstan-3-one (134) with 1-chloroethyl phenyl sulfone provides an epoxy sulfone (135), which is cleaved by MgBr2 to give a 99 1 mixture of 3-acetyl-3-bromoandrostanes (136 and 137 equation 33), whereas similar treatment of 17-p-hydroxy-5-B-androstan-3-one (138) gives a 4 96 mixture of 3-acetyl-3-bromoandrostanes (139 and 140 equation 34). These facts may reflect the steric course of the initial attack of the a-sulfonyl carbanion on the carbonyl face. 

Acetylenic ketones are useful intermediates in terpenoid synthesis. Coke and co-workers have described a novel synthesis of acetylenic ketones, inspired by, but different from, the Eschenmoser fragmentation. The procedure is illustrated in Scheme 34 by its application to the synthesis of exo-brevicomin (134) the pheromone from Dendroctonus brevicomis. Hydroboration of the double bond of oct-l-en-4-yne with 9-BBN, followed by the acetylene zipper procedure, and base-induced alkyl transfer to t-butyl bromo-methyl ketone offers an efficient route to acetylenic ketones in greater than 70% yield [(135)->(136)]. °... 

Transition metal-catalysed carbene abstraction has been reported once, whereby a-oxo Au carbenes generated on oxidation of terminal alkynes are prone to abstract halogen from solvents such as 1,2-dichloroethane and 1,2-dibromoethane. This method constitutes an attractive approach for preparing chloro- or bromo-methyl ketones in one step starting from terminal alkynes. 

Naphthoic acid has been prepared principally by the hydrolj sis of d-naphthonitriled the overall yields from (3-naph-thylamine, from sodinm-/3-naphthalene sulfonate, and from calcium d-naphthalene sulfonate being given as (approximately) 20 per cent, 21 per cent, and 50 per cent, respectively. The acid has been prepared also by the carbonation of the Grignard reagent from the less accessible /3-bromo derivative and. more recendy, from the readily available methyl ketone. ... 

Pure 2-amino-5-bromo-3-nitropyridine, yellow needles, m.p. 210°, may be obtained by recrystallizing the product from ethyl methyl ketone. 

Btomomethyl ketones. Direct bromination of methyl ketones as a route to bromomethyl ketones is usually unsatisfactory because bromine mainly attacks the more substituted carbon. One expedient is reaction of ketals of the ketone with phenyltrimethylammonium perbromide (1,855) or with bromine in methanol. Actually methyl ketones can be brominated directly with bromine in methanol, but the regiospeciflcity depends on the structure of the ketone. Thus l-bromo-3-methyl-2-butanone (2) can be obtained directly from (1) in good yield as shown in equation (I). It should be noted that dimethyl ketals are formed as well and must be hydrolyzed during work-up. ... 

The application to the saturated methyl ketone (83) of Wilds method of constructing ring D (Scheme 10) gave derivatives of 16-oxoestrone [188] (see Scheme 6). The alkylation of ketone (83) with bromoacetic ester and the reaction of the chloride of the acid formed (103) with sodiomalonic ester and decarboxylation led to the diketone (104). An attempt at its direct synthesis from ketone (83) by alkylation of the latter with chloro- or bromo-acetone was unsuccessful. The intramolecular cyclization of ketone (104) by the action of alkali yielded the -ketone (107), hydrogenation of which led to the isolation of one isomer of the 16-ketone (106) of unknown configuration [188]. The construction of a side chain at C14 of the methyl... 

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