| 摘要 |
1356373 Preparation of 6α,21-difluoro-20- keto pregnanes SYNTEX CORP 21 April 1972 [26 May 1971] 18733/72 Heading C2U 6α,21 - Difluoro - 20 - keto - pregnanes are prepared by treating corresponding 21-bromo- 6α-fluoro-20-keto-pregnanes with an alkali metal fluoride selected from potassium, cesium and rubidium fluorides in tetramethylenesulphone. This process is particularly applicable to the following synthesis of 9α,11#-dichloro-6α,21- difluoro - 16α,17α- alkylidenedioxy - 3,20 - diketo - pregn - 4 - enes and - pregna - 1,4 - dienes wherein Ac is C 2-12 acyl; R is C 1-7 alkyl or is alkaryl; R<SP>1</SP> and R<SP>2</SP> are each H or C 1-7 alkyl, or together with the adjacent carbon atom form a cycloalkyl group of 5-7 ring atoms; and #<SP>1</SP> is optional. The 21-bromo steroids are prepared by heating the 21-alkyl- or -alkaryl-sulphonates with an alkali metal bromide in an inert solvent. The 21-fluorination is typically effected at 100- 135‹ C.
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