Desymmetrization intermolecular

Brase reported an intramolecular asymmetric Heck-intermolecular Heck cascade reaction of l,3-bis(enolnonaflates) 131 to the highly congested bicyclic compound 132 [122] (Scheme 5). Although the level of asymmetric induction is low (up to 52% ee), this result shows that the concept of two leaving groups in the desymmetrization reaction can be applied. 

Intermolecular aldol reaction [6.2.1] Desymmetrization of meso epoxides [13.4]... 

On the basis of the desymmetrization concept, the kinetic optical resolution of a racemic substrate [66] can be recognized as an intermolecular version of desymmetrization. The kinetic resolution of a racemic allylic ether by the glyoxylate-ene reaction also provides efficient access to remote but relative [64] asymmetric induction. The reaction of allylic ethers catalyzed by the (f )-BINOL-derived complex (1) provides the 2R,5S)-syn products with > 99 % diastereoselectivity and > 95 % ee (Sch. 18). The high diastereoselectivity, coupled with the high ee, strongly suggests that the cata-lyst/glyoxylate complex efficiently discriminates between the two enantiomeric substrates to accomplish the effective kinetic resolution. In fact, the relative rates of the reactions of the enantiomers, calculated by use of the equation ... 

On the basis of the desymmetrization concept, the kinetic optical resolution of a racemic substrate [42a, 42b] might be recognized as an intermolecular version of the desymmetrization. The kinetic resolution of a racemic allylic ether by the glyoxylate-ene reaction also provides an efficient access to remote but relative... 

C-H bonds. This strategy has been used in an intramolecular fashion for the oxidation of hydrocarbons (eq 49) and steroids. Fructose-derived ketone 5 has also been used for this purpose in an intermolecular reaction for the desymmetrization and kinetic resolution of 1,2-diols to a-hydroxy ketones (eq 50). There has also been a report of the direct oxidation of hydrocarbons to ketones and lactones by Mn-porph)rin complexes with Oxone. ... 

Scheme 18.10 Desymmetrization of cyclohexadienones, according to Rovis and coworkers. 18.2.2.2 Intermolecular Stetter Reactions...

Both intermolecular and intramolecular asymmetric Heck reactions are known. For the latter, an example is the desymmetrization of decaline systems (Scheme 5-38). ° In this case, JOSIPHOS (Figure 5-9) is a suitable ligand and gave the best enantioselectivities. 

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