ISSN:
0009-2940
Schlagwort(e):
Zirconocene complexes
;
(Metaloxy)carbene complexes
;
Template reaction, organometallic
;
Steroid side-chain attachment
;
Chemistry
;
Inorganic Chemistry
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
Notizen:
The reaction of (butadiene)zirconocene with hexacarbonyltungsten gives the metallacyclic [(π-allyl)zirconoxy]carbene complex 7. This reagent adds to a variety of ketones to yield chiral nine-membered metallacyclic ring systems (8). These systems are thus formed by means of 1,4-selective coupling reactions of 1,3-butadiene with W(CO)6 and an organic carbonyl compound at the zirconocene template. The ketones subjected to react with 7 include benzophenone, methyl vinyl ketone, cyclopentanone, and 3-methoxyestra-1,3,5(10)-trien-17-one (12). The coupling products of 7 with cyclopentanone (8c) and 12 (8d-A) were characterized by X-ray crystal structure analyses. Of the four possible diastereomeric nine-membered metallacyclic coupling products of 7 with 12 a single isomer [8d-A with (13'S,17'R,2,3,4-pS) configuration] was formed with ≥98% selectivity and isolated in 95% yield. Treatment of the complexes 8 in tetrahydrofuran with water and pyridine N-oxide very effectively removed both transition metals with the formation of the corresponding β,γ-unsaturated ε-hydroxy carboxylic acids. The overall reaction sequence has thus converted the steroid ketone 12 very selectively to 5-[3-methoxy-17β-hydroxyestra-1,3,5(10)-trien-17α-yl]-(E)-pent-3-enoic acid (10d)
Zusätzliches Material:
2 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/cber.19931260923
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