Intramolecular Horner-Emmons condensation

An efficient and regioselective method for the synthesis of pharmaceutically important intermediates (323) has been developed. It is based on the intramolecular Wadsworth-Horner-Emmons condensation of monocyclic compound (322), which is available by a selective stepwise functionalization of pyrazolidinone (321) (Scheme 64). The overall yield is about 25% <90TL2805>. 

An extremely elegant route to pyrazoles which allows control over all three substituents, involves forming a ring closure precursor by Horner/Emmons condensation of a tosylhydrazone-phosphonate with an aldehyde, which become the 5-substituent intramolecular Michael addition and then loss of toluenesulfinate as the final aromatising step, completes the sequence. 

Intramolecular phosphonate-ketone condensation (Horner- Wadsworth-Emmons)... 

A tandem enzymatic aldol-intramolecular Homer-Wadsworth-Emmons reaction has been used in the synthesis of a cyclitol.310 The key steps are illustrated in Scheme 8.33. The phosphonate aldehyde was condensed with dihydroxyacetone phosphate (DHAP) in water with FDP aldolase to give the aldol adduct, which cyclizes with an intramolecular Horner-Wadsworth-Emmons reaction to give the cyclo-pentene product. The one-pot reaction takes place in aqueous solution at slightly acidic (pH 6.1-6.8) conditions. The aqueous Wittig-type reaction has also been investigated in DNA-templated synthesis.311... 

The starting materials, frans-3,4-methylenedioxycinnamyl alcohol (61a) and frans-2-methoxy-3,4-methylenedioxycinnamyl alcohol (61b) were prepared from the corresponding benzaldehyde via substituted ethyl cinnamate by means of the Horner-Emmons reaction and lithium aluminium hydride reduction. Condensation of compound (61 a) or (61 b) with compound (47) gave compound (62a) or (62b), respectively, followed by ring closure to afford compound (63a) or (63b). Intramolecular Diels-Alder reaction of compound (6 2) led to the formation of the aromatized compounds as by-product in both cases. Moreover, in the reaction of... 

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