C-Dialkylation of Meldrum's acid
(2a) and 5-benzyl Meldrum's acid (2b) can be
achieved through
Mitsunobu dehydration using allylic and arylmethyl alcohols as
alkylating agents. This is the
first time that the Mitsunobu reaction is successfully applied to the
C-alkylation of a highly
enolizable cyclic β-dicarbonyl system. With primary (allylic and
arylmethyl) alcohols, the alkylations
always take place at the carbon bearing the hydroxy group. For
secondary allylic alcohols, a catalytic
amount of Pd(0) must be added to enhance the regioselectivity of
C-alkylation over O-alkylation.
With (Ph3P)4Pd(0) as a catalyst,
the reaction occurs specifically at the less hindered carbon,
and
the configuration of the resultant double bond is always
trans. Attempts to monoalkylate Meldrum's
acids 2a and 2b failed.
Mitsunobu C-Alkylation of Meldrum's Acids. -For the first time the Mitsunobu reaction is applied to the C-alkylation of a highly enolizable cyclic β-dicarbonyl system. With primary alcohols the alkylations take place at the carbon bearing the hydroxy group. For secondary alcohols a catalytic amount of Pd (0) must be added to enhance the regioselectivity of C-alkylation over Oalkylation. Attempts to monoalkylate Meldrum's acids fail. -(SHING, T. K. M.; LI, L.-H.; NARKUNAN, K.; J.
Stereochemistry of Osmylation of Chiral Dienes: Diastereoselective Synthesis of Octitols. -The usefulness of the osmylation of sugar-derived dienes such as (III) for the synthesis of higher sugars such as (V), (VI) and (VII) is shown. -(NARKUNAN, K.; NAGARAJAN, M.; J. Chem. Soc., Chem.
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