Wittig rearrangement simple diastereoselectivity

Wittig rearrangements of alkynyl ethers follow the stereochemical trends demonstrated by other w-donor-stabilized substrates, and simple diastereoselection is typically excellent for both E- and Z-substrates 37 " 39. Propargyl-stabilized anions of E- and Z-crotyl ethers 27 exhibit high levels of simple diastereoselection. 

Benzyl ethers were among the first [2,3] Wittig substrates for which self-immolalive chirality transfer was documented46. Thus, rearrangement of benzyl ether 50 proceeds with excellent 1,3 chirality transfer, but essentially no simple diastereoselection. 

A similar substrate-induced 1,2 and 1,3 diastereoselection has been described for the [2,3] Wittig rearrangement of a series of allyloxy acetates 18 80. As in the case of propargyl-stabilized systems, Z-olefins 18 undergo rearrangement with excellent simple and induced diastereoselection to afford major products which compose > 98 % of the product mixture. The correspond-... 

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