Intramolecular Chromium(II)-Catalyzed Pinacol Cross Coupling of 2-Methylene-α,ω-dicarbonyls
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چکیده
SYNLETT 2004, No. 6, pp 1054–105806.05.2004 Advanced online publication: 25.03.2004 DOI: 10.1055/s-2004-822895; Art ID: G04404ST © Georg Thieme Verlag Stuttgart · New York Abstract: Using only 10% of CrCl2 as catalyst, manganese-powder as reducing agent and TMSCl as scavenger, 2-methylene-a,w-dialdehydes and -ketones can be coupled to form cyclic diols diastereoselectively. The diastereomeric excess strongly depends on the ring size and the substituents of the w-carbonyl group. The greater the ring size the higher diastereoselectivities are observed. In all cases cis-diols are preferentially formed.
منابع مشابه
Influence of chelating silyl scavengers on the diastereoselectivity of chromium catalyzed pinacol cross couplings
The choice of the silyl scavenger shows a substantial influence on the diastereoselectivity of the chromium catalyzed pinacol cross coupling. In the case of the intramolecular cyclization, two competing effects are observed. If the silylation reagents contain chelating heteroatoms in the side chain, a remarkable trans-selectivity is observed. Conversely the cis-diols are preferred if bulky subs...
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