P-Elimination Strategy and Miscellaneous Approaches

Typical Experimental Procedure To freshly prepared LiNH2 (prepared in situ by dissolving 12mg atoms of lithium metal) in hquid NH3 (30mL) at -33°C was added a solution of chloride (1) (2 mmol) in THF (2mL) for 3 minutes, after which solid NH4CI was added and ammonia was evaporated. The residue was partitioned between water and ether and the ether layer was dried and concentrated to obtain the residue, which was purified by silica-gel column chromatography to get pure 2 in 90% yield. 

It was also observed that controlled addition of base would allow one to isolate the vinyl chloride, which could further participate in Pd-catalyzed coupling reactions. This methodology offers an advantage by providing both possible enantiomers, as the Sharpless asymmetric epoxidation works equally efficiently with (+)-DlPT and (-)-DlPT. The P-elimination strategy is also well exploited with sugar derivatives and Sharpless diols. 

In this chapter we have highlighted several practical approaches for the synthesis of chiral propargyl alcohols by various methods, the most practical ones being the asymmetric alkynation of carbonyl compounds in the presence of chiral auxiliaries and the p-eUmination of stereochemically well-defined a,p-dioxyhalides. These two approaches have been utilized efficiently in the synthesis of several bioactive natural products. 

The authors thank T. V. Pratap, P. V. R. Reddy, and B. N. Babu for helping in preparing the manuscript. 

Takano, S. Smaizu, K. Sugihara, T. Ogasawara, K. Chem Commun., 1989, 1344. 

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