Alkenes catalytic enantioselective alkylation

Catalytic Enantioselective Alkylation of Alkenes with Alkylmagnesium Halides... 

Zhang L, Le CM, Lautens M (2014) The Use of silyl ketene acetals and tmol ethers in the catalytic enantioselective alkylative ring opening of oxa/aza bicyclic alkenes. Angew Chem... 

The catalytic enantioselective addition of vinylmetals to activated alkenes is a potentially versatile but undeveloped class of transformations. Compared to processes with arylmetals and, particularly alkylmetals, processes with the corresponding vinylic reagents are of higher synthetic utility but remain scarce, and the relatively few reported examples are Rh-catalysed conjugate additions. In this context, Hoveyda et al. reported very recently an efficient method for catalytic asymmetric allylic alkylations with vinylaluminum reagents that were prepared and used in Thus, stereoselective reactions... 

Recently, Jorgensen reported the first example of a catalytic enantioselective vinylic substitution reaction (Scheme 11.14). With a bulky 1-adamantylcarbonyl group modified phase-transfer catalyst lOd as the catalyst, the reaction between alkyl cyclopentanone-2-carboxylates (53a) with (ZJ-P-cholro-l-phenylpropenone (63a) proceeded smoothly, affording the product 64a with Z/f > 95 5 and 94% ee [50]. As for the trisubstituted alkene 64b, the a-iodine atom was tolerated in the catalytic reaction. 

Alkylated diphosphines (R,R)-(92) and (93) were used as chiral ligands in the Pt-catalyzed hydroformylations of some alkeneic substrates. These ligands bring about a loss of catalytic activity with respect to the corresponding diphenylphosphine homolog, particularly in the case of the platinum systems. The regioselectivity favors the straight-chain (or less branched) isomer in the case of terminal alkenes with the exception of styrene the enantioselectivity is very low in all cases.320... 

The studies summarized above clearly bear testimony to the significance of Zr-based chiral catalysts in the important field of catalytic asymmetric synthesis. Chiral zircono-cenes promote unique reactions such as enantioselective alkene alkylations, processes that are not effectively catalyzed by any other chiral catalyst class. More recently, since about 1996, an impressive body of work has appeared that involves non-metallocene Zr catalysts. These chiral complexes are readily prepared (often in situ), easily modified, and effect a wide range of enantioselective C—C bond-forming reactions in an efficient manner (e. g. imine alkylations, Mannich reactions, aldol additions). 

A catalytic asymmetric oxidation of mono-, di-, and tri-substituted alkenes using a chiral bishydroxamic acid (BHA) complex of molybdenum catalyst in air at room temperature leads to good to excellent selectivity. It has been suggested that the Mo-BHA complex combines with the achiral oxidant to oxidize the alkene in a concerted fashion by transfer of oxygen from the metal peroxide to the alkene.78 The chiral BHA-molybdenum complex has been used for the catalytic asymmetric oxidation of sulfides and disulfides, utilizing 1 equiv. of alkyl peroxide, with yields up to 83% and ees up to 86%. An extension of the methodology combines the asymmetric oxidation with kinetic resolution providing excellent enantioselectivity (ee = 92-99%).79... 

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