Regioselektive Reaktionen an der 17-Oxogruppe von Androsta-1,4-dien-3,17-dion nach in-situ-Schutz mit Titantetrakis(dimethylamid)
✍ Scribed by Müller, Andreas ;Beckert, Rainer ;Schönecker, Bruno ;Weiß, Dieter
- Publisher
- John Wiley and Sons
- Year
- 1993
- Tongue
- English
- Weight
- 703 KB
- Volume
- 1993
- Category
- Article
- ISSN
- 0947-3440
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✦ Synopsis
Regioselective Reactions at the 17‐Oxo Group of Androsta‐1,4‐dine‐3,17‐dione after in situ Protection with Titaniumtetrakis(dimethylamide)
After in situ protection of androsta‐1,4‐diene‐3,17‐dione (1) with titaniumtetrakis(dimethylamide) (10) at −20°C to −30°C, the lithium enolates of methyl methoxyacetate (2a) and ethyl acetate (2b) react regio‐ and stereoselectively at the 17‐position to give the 17‐hydroxy‐17α‐pregnanes 12 and 6. Dehydration of 12 and 6 furnishes the 17(20)‐olefins 13 and 14, intermediates for the synthesis of corticoids and gestagens. The reaction of 1 with 10 and 2a at −60°C gives byproducts of a dienone‐benzene rearrangement of the A‐ring. The reactions of 1 with 2a and 2b without titaniumtetrakis‐(dimethylamide) (10) proceed regioselectively at the 3‐position or nonregioselectively at the 3‐ and 17‐positions, respectively.