In the Wittig rearrangement

In the Wittig rearrangement, an anion derived from an ether rearranges to the salt of an alcohol. 

Eisch, J. J., Kovacs, C. A., Rhee, S.-G. Rearrangements of organometallic compounds. X. Mechanism of 1,2-aryl migration in the Wittig rearrangement of a-metallated benzyl aryl ethers. J. Organomet. Chem. 1974, 65, 289-301. 

Any reaction that forms a bond between two prochiral atoms in a stereoselective manner is a valuable synthetic method. Some of the natural products that have been made in nonracemic form using the [2,3]-Wittig rearrangement as the key step are illustrated in Figure 6.7. The stereocenters formed in the Wittig rearrangement are indicated ( ). 

Knowledge of the cyclization rate of the 5-hexenyl radical has also been used to study cage reactions of alkyl radicals generated in solution from diacyl peroxides or to distinguish between intra- and intermolecular pathways in the Wittig rearrangement. It has also been used to study the mechanism of the deshalogenation of 1,4-, 1,5-, and 2,3-dihaloalkanes by alkali... 

The stereochemistry of the Wittig rearrangement can be predicted in terms of a cyclic five-membered TS in which the a-substituent prefers an equatorial orientation.293... 

Medium sized carbocycle synthesis Ring contracting [1,2]-Wittig rearrangement Yadav and Ravishankar have demonstrated that the Wittig rearrangement of the cyclic substrate 32 is useful for the construction of the taxane skeleton 33, albeit in low yield (equation 17). ... 

The [2,3] sigmatropic rearrangement pattern is also observed with anionic species. The most important case for synthetic purposes is the Wittig rearrangement, in which a strong base converts allylic ethers to a-allyl alkoxides.191... 

Asymmetric Wittig rearrangement (12, 96). The Wittig rearrangement has been used to control the configuration of two of the four chiral centers in a synthesis... 

This stability order has been used in a reevaluation of the mechanism of the Wittig rearrangement of alkyl benzyl ethers (Eq. (82)). The migration... 

Wittig rearrangement has been used in a diastereoselective total synthesis of the triester of viridiofungin.10 The Wittig rearrangement of 17(20)-ethylidene-16- (g) furfuryloxy steroids (8) has provided natural and unnatural 22-hydroxy steroids (9), (10), and (ll).11... 

The Wittig rearrangement is primarily used in the transformation of an allylic ether to an a-allyl alcohol (Scheme 26.18).444-445 The transition-state geometry plays an important role to determine the reaction outcome that, in turn, is dependent on the stereochemistry of the double bond (Figure... 

The Wittig rearrangement has been used in the synthesis of a wide range of compounds that rely on this versatile protocol,455 ranging from large antibiotics,456-457 to dihydrofurans,458459 to steroid derivatives.460 62 However, the use of strongly basic conditions is the major hindrance to the implementation of this reaction at scale. 

The acid was then converted to its acid chloride (XXXVII), thence to the diazoketone (XXXVIII), and finally to the acid (XXXIII) by Wolff rearrangement as shown below. Its endo configuration and the structures of the epimeric acids obtained in the Wittig reaction sequence are thereby established. 

Where the Wittig rearrangement provides products formed with retention of the configuration at the anomeric center, the use of carbenoids in the formation of C-glycosides provides a complementary... 

Unequalled in elegance is the double Still-Wittig rearrangement of (48), which gave the bis-(ZZ)-homoallylic alcohol (49) in 95% isomeric purity (equation 16). (Z)-Selectivity has also been noted for the Wittig rearrangement of an acid dianion (equation 17). ... 

---