781647-79-8Relevant articles and documents
Highly diastereoselective arylation of (S)-mandelic acid enolate: Enantioselective synthesis of substituted (R)-3-hydroxy-3-phenyloxindoles and (R)-benzylic acids and synthesis of nitrobenzophenones
Barroso, Santiago,Blay, Gonzalo,Cardona, Luz,Fernandez, Isabel,Garcia, Begona,Pedro, Jose R.
, p. 6821 - 6829 (2007/10/03)
An easy access to substituted (R)-3-hydroxy-3-phenyloxindoles, (R)-benzylic acids, and benzophenones is described. The reaction of the lithium enolate of the (2S,5S)-cis-1,3-dioxolan-4-one derived from optically active (S)-mandelic acid and pivalaldehyde with several o- and p-halonitrobenzenes proceeds readily to give the corresponding arylation products in good yields and diastereoselectivities. The reduction of the nitro group with Zn/HCl/EtOH in the o-nitro arylation products with concomitant intramolecular aminolysis of the dioxolanone moiety leads directly to enantiomerically pure (R)-3-hydroxy-3- phenyloxindoles. On the other hand the basic hydrolysis of the dioxolanone moiety in all the arylation products (ortho and para) leads to enantiomerically pure substituted (R)-benzylic acids. The oxidative decarboxylation of these latter with oxygen as terminal oxidant in the presence of pivalaldehyde and the Co(III)-Me2opba complex as catalyst gives substituted nitrobenzophenones.
