2-cyclopentenone nitroalkane

The Nef reaction can also be carried out with reducing agents. Aqueous titanium chloride reduces nitro compounds to imines, which are readily hydrolyzed to carbonyl compounds (Eq. 6.17).28 The Michael addition of nitroalkanes to enones followed by reaction with TiCl3 provides an excellent route to 1,4-diketones and hence to cyclopentenones. For example, cw-jasmone is readily obtained,28 as shown in Eq. 6.18. 

Because the a-nitroketones are prepared by the acylation of nitroalkanes (see Section 5.2), by the oxidation of (3-nitro alcohols (Section 3.2.3), or by the nitration of enol acetates (Section 2.2.5), denitration of a-nitro ketones provides a useful method for the preparation of ketones (Scheme 7.10). A simple synthesis of cyclopentenone derivatives is shown in Eq. 7.66.76... 

Further uses of nitroalkanes are in 1,4-additions (Michael reaction) to a,p-unsaturated carbonyl compounds and the like. Recent reports deal with transformations of 1,4-nitro ketones, 7, into 1,4-keto aldehydes, 8, and cyclization to cyclopentenones.16... 

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