Uses of Phosphoranes in Organic Synthesis

Reagents i, (COCO2, ii, R SH-EtaN iii, PhaP-CCU iv, excess CCU v, MeCN 

A number of reactions of phosphorus pentachloride (78) with carbonyl compounds have been reported. a-Hydroxycarboxylic acids, such as malic and tartaric acids, react with (78) to give phosphorodichloridates with general part-structure (110). The heterocyclic hydrazide (111) is converted into the cyanide (112), and hence into the isomer (113), by treatment with (78) in refluxing benzene.  

Other reactions of (78) described in the literature include that with /3-maltose octa-acetate, and with 4-acetylisochroman-l,3-dione. The use of phosphorus pentafluoride in the polymerization of THF has been investigated.  

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Uses of Phosphoranes in Organic Synthesis.— Triphenylphosphine dihalides (107) have been used to achieve cis-trans isomerization of simple alkenes, as shown in Scheme 9. The key to the sequence is that epoxides undergo a net c/j-addition of halogen on... 

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