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 beta-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 (Ph(3)P)(4)Pd(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.
作者:Tony K. M. Shing、Lian-Hai Li、Kesavaram Narkunan
DOI:10.1021/jo962288+
日期:1997.3.1
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 beta-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 (Ph(3)P)(4)Pd(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.
Dendronized Polymer Organogels from Click Chemistry: A Remarkable Gelation Property Owing to Synergistic Functional-Group Binding and Dendritic Size Effects
作者:Kwun-Ngai Lau、Hak-Fun Chow、Man-Chor Chan、Ka-Wai Wong