Hydrogen bromide with diazo ketones

The reaction232-235 (see also Ref. 236) of 1-diazoketones with hydrogen fluoride that affords 1-fluoro ketones has also been applied to carbohydrates, with, however, no success. Treatment of 3,4-di-O-benzoyl-1-deoxy-l-diazo-D-gfycero-tetrulose with hydrogen fluoride in ether mainly afforded 3,4-di-O-benzoyl-D-gfycero-tetrulose, whereas, with hydrogen bromide and chloride, 3,4-di-O-benzoyl-l-bromo-l-deoxy-and 3,4-di-O-benzoyl-l-chloro-l-deoxy-D-gfycero-tetrulose, respec-... 

The starting material in the synthesis of 106 (157) was 3-(3,4-dimethoxy-phenyl)propanoyl chloride, which with the aid of diazomethane at — 20°C, was converted to the diazo ketone 108. Treatment of 108 in ether with 48% hydrogen bromide gave 4-bromo-l-(3,4-dimethoxyphenyl)-3-pentanone (109). The bromo ketone 109 was heated in an autoclave with 2-iminotetra-hydropyran hydrochloride in methanolic ammonia and yielded the product 106, identical to the alkaloid cypholophine, in an overall yield of 6%. 

Diazo ketones are transformed to a-bromo ketones on treatment with hydrogen bromide (equation... 

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