2-formylcyclopropane derivatives

A domino Michael/a-alkylation reaction between bromoacetoacetates and a,fS-unsaturated aldehydes provides the 2-formylcyclopropane derivatives in high yields with excellent diastereoselectivity and up to 99% ee (for further details see Chapter 10) [37]. Similarly, an approach using enones 45 and bromonitromethane 46 has been used in organocatalytic nitro-cyclopropanation reaction to give 47 (Scheme 7.8)... 

In contrast to the use of the specific type of sulfur ylides and related compounds, the employment of readily available alkyl halides for a catalytic Michael-alkylation reaction with enals to produce the corresponding formal [2-1-1] cycloadducts is an extremely challenging task. As an example, Wang [82a] and Cordova [82b, 83a] independently reported the enantioselective organocatalytic reaction of bromoma-lonates 78 and enals, which led to the corresponding cyclopropanes 79. In both cases, chiral diarylprolinol trimethylsilyl ethers 8 and 80 were involved as catalysts, giving access to the corresponding 2-formylcyclopropane derivatives 79 in... 

As is the case for oxycyclopropanes extra activation and extended product functionality is achieved by using sulphur-substituted cyclopropanes with a vicinal acceptor group. According to equation 116 synthesis of a variety of y-oxothioesters and j -oxoketene dithioacetals is possible. A formylcyclopropane of this type has been converted to a furan derivative " . Transformation of the carbonyl to a hydroxymethyl group and acid treatment allows preparation of dienes " ... 

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