Samarium-Promoted Cyclopropanation of Allylic Alcohols
The use of samarium/mercury amalgam in conjunction with diiodomethane or chloroiodomethane to generate samarium carbenoids for the efficient cyclopropanation of allylic alcohols is discussed.These hydroxyl-directed cyclopropanations occur under mild conditions and allow a wide range of substitution about both the olefin and the carbinol carbon in allylic alcohol substrates.High yields and high diastereoselectivities are observed for many substrates.
Diastereoselective manipulations of bicyclo[m.1.0]alkane derivatives. 2. Nucleophilic additions to the carbonyl carbons of bicyclot[m.1.0]alkan-2-ones
Enantiomerically enriched bicyclo[m.1.0]alkan-2-ones having larger ring sizes between five and 16 members were prepared and subjected to additions of nucleophiles to the carbonyl carbon. Such additions were efficient and highly diastereoselective for all nucleophiles for bicycles with ring sizes greater than seven. Diastereoselectivity for these additions is rationalized by assuming early transition states and exposure of the same carbonyl face to the ring exterior in the vast majority of populated conformers for each bicyclic ketone.
Mash, Eugene A.,Gregg, Timothy M.,Kaczynski, Michelle A.
p. 2743 - 2752
(2007/10/03)
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