Reactions with a, 3-Unsaturated Carbonyl Compounds

Trialkyl phosphites readily undergo conjugate addition with a,(3-unsaturated carbonyl compounds in the presence of a proton source, such as a protic solvent.359 The use of a protic solvent, such as an alcohol, obviates the difficulties found in the performance of the simple Abramov-type reaction with a,(3-unsaturated carbonyl compounds.189198 In alcohol medium, an ether is generated as a by-product in the dealkylation process (Equation 3.22). 

Allenamide 188 having a chiral auxiliary was successfully applied to stereoselective [4+2]-cycloaddition reactions with a,/3-unsaturated carbonyl compounds at 80 °C to give pyranyl heterocycles with high enantioselectivities [153],... 

In reactions with a,(3-unsaturated carbonyl compounds, the organocopper reagents prefer 1,4-over 1,2-addition. 

The present review will, because of the complexity of the Grignard reagents, begin with a discussion of some physical and chemical properties of the reagents. Section 1.3 is concerned with the reactions of benzophenone with Grignard reagents. This is because benzophenone has, for many years, been a favourite substrate for researchers in the field and because observations made with benzophenone are valuable for the understanding of other reactions. Section 1.4 deals with concerted reaction mechanisms with carbonyl compounds. Section 1.. ) concerns reactions with a. /3-unsaturated carbonyl compounds and Section 1.6 concerns non-carbonylic substrates which react by stepwise radical type mechanism .. 

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