Michael Additions Investigated in Micro Reactors

Organic synthesis 52 [OS 52] Addition of2,4-pentanedione enolate to ethyl propiolate [8] 

The reactions [OS 52], [OS 53], [OS 54] and [OS 55] were chosen as test reactions among a wide class of reagents employed for Michael additions. 1,3-Dicarbonyl compounds were chosen because of their relatively high acidity since they enable one to use weak bases instead of strong bases such as sodium efhoxide. The latter is labile to moisture and can react with the Michael acceptor [8]. Diisopropylethyl-amine was chosen as a weak base. 

The corresponding batch operation protocol refers to the following procedure [8], The 1,3-dicarbonyl compoimd (0.25-0.50 g 1.5-5.0 mmol) was added to a stirred solution of ethyl propiolate (0.15-0.49 g 1.54—5.0 mmol) and diisopropylefhylamine (0.40-1.29 g 3.00-10.00 mmol) in ethanol (50 ml). After stirring overnight, the reaction mixture was concentrated and purified by silica gel chromatography. 

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