195508-14-6Relevant academic research and scientific papers
Synthesis of vinyl 1,2-diketones
Habel, Lothar W.,De Keersmaecker, Sigrid,Wahlen, Joos,Jacobs, Pierre A.,De Vos, Dirk E.
, p. 4057 - 4059 (2007/10/03)
A new route is outlined for preparation of vinyl 1,2-diketones via a three-step sequence. First, allylic alcohols are photooxidized by 1O2 to hydroperoxides, which are reduced to vinyl 1,2-diols. These vinyl 1,2-diols are oxidized to vinyl 1,2-diketones with oxoammonium salts, which are prepared in situ from organic nitroxyl radicals. The new route is short, avoids the use of protecting groups, and is generally applicable to obtain aliphatic or aromatic vinyl 1,2-diketones.
Stereoselective synthesis of 3(2H)-dihydrofuranones by addition of lithiated methoxyallene to chiral aldehydes
Hormuth,Reissig
, p. 67 - 73 (2007/10/02)
Lithiated methoxyallene 2 adds to chiral aldehydes such as 2- phenylpropanal and N,N-dibenzylated α-amino aldehydes 4-8 to give products 9-14 in good yields and with excellent anti-selectivity. The stereochemical outcome of these reactions can be explained by the Felkin-Anh model in a straightforward manner. The crude reaction products can either be transformed to enones by hydrolysis with acid or be converted into 2,5-dihydro-3- methoxyfuran derivatives 19-24 by treatment with potassium tert-butoxide in DMSO. The latter can be hydrolyzed to give 3(2H)-dihydrofuranones 25-29. The diastereoselectivity of the initial addition step is transferred to the dihydrofuran derivative without a major change in the isomer ratio. Compounds derived from α-amino aldehydes 5, 6, and 8 are assumed to be enantiomerically pure. Sodium borohydride reductions of and Grignard additions to 3(2H)-dihydrofuranones 27a and 28a demonstrate that these chiral ketones react in a highly diastereoselective manner. In summary, this paper shows that lithiated methoxyallene 2 can serve as a very useful equivalent for α,β-unsaturated acyl anions and 1,3-dipolar synthons in asymmetric synthesis.
