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Regioselektive Reaktionen an der 17‐Oxogruppe von Androsta‐1,4‐dien‐3,17‐dion nach in‐situ‐Schutz mit Titantetrakis(dimethylamid)
Author(s) -
Müller Andreas,
Beckert Rainer,
Schönecker Bruno,
Weiß Dieter
Publication year - 1993
Publication title -
liebigs annalen der chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 0170-2041
DOI - 10.1002/jlac.1993199301209
Subject(s) - regioselectivity , chemistry , in situ , stereochemistry , medicinal chemistry , dehydration , organic chemistry , catalysis , biochemistry
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.