Tartrate, diisopropyl

A number of reaction variables or parameters have been examined. Catalyst solutions should not be prepared and stored since the resting catalyst is not stable to long term storage. However, the catalyst solution must be aged prior to the addition of allylic alcohol or TBHP. Diethyl tartrate and diisopropyl tartrate are the ligands of choice for most allylic alcohols. TBHP and cumene hydroperoxide are the most commonly used terminal oxidant and are both extremely effective. Methylene chloride is the solvent of choice and Ti(i-OPr)4 is the titanium precatalyst of choice. Titanium (IV) t-butoxide is recommended for those reactions in which the product epoxide is particularly sensitive to ring opening from alkoxide nucleophiles. ... 

Epoxidation of the simplest allylic alcohol, allyl alcohol 7, is achieved in 88-92% ee with yields of 50-60% using diisopropyl tartrate as ligand. In situ derivatization of the product glycidol 8 via esterification, sulfonylation, or ring opening with nucleophile is an attractive alternative to isolating glycidol. 

DIPT diisopropyl tartrate SAE Sharpless Asymmetric Epoxidation... 

Solutions of 7.5 g (40 mmol) of triisopropyl borate in 10 mL of dry diethyl ether and 40 mmol of 0.87 M allylmagnesium bromide in diethyl ether arc added dropwisc separately to 10 mL of diethyl ether at — 78 °C. This mixture is stirred for 0.5 h at —78 JC, then is allowed to warm to r.t. and stirred for 3 h. The slurry is recooled to 0 C. and then 40 mmol or 1 N aq hydrochloric acid saturated with NaCl are added dropwise over 15 min. The mixture is warmed to r.t., and stirring is continued for 10 min. The organic layer is separated and directly treated with 9.4 g (40 mmol) of diisopropyl (/ ,/ )-tartrate (DIPT). The aqueous phase is extracted with three 50-mL portions of diethyl elher/CH.CI, 5 1. The combined organic layers are dried over anhyd MgS04 for 2.5 h, then filtered under argon. The filtrate is concentrated in vacuo and toluene is added to give a final volume of 50 mL. The concentration of reactive allylboronate is determined by treatment of a 1 mL aliquot of this solution with a known excess of cyclohexanecarboxaldehyde. This... 

The synthesis in Scheme 13.49 features use of an enantioselective allylic boronate reagent derived from diisopropyl tartrate to establish the C(4) and C(5) stereochemistry. The ring is closed by an olefin metathesis reaction. The C(2) methyl group was introduced by alkylation of the lactone enolate. The alkylation is not stereoselective, but base-catalyzed epimerization favors the desired stereoisomer by 4 1. 

It has recently been found that Et2Zn promotes the 1,3-dipolar cycloaddition of nitrile oxides to allyl alcohol in the presence of catalytic amounts of diisopropyl tartrate (DIPT). By this method, 2-isoxazlines are obtained in good yields and up to 96% ee (Eq. 8.73).124a A positive nonlinear effect (amplification of ee of the product) has been observed in this reaction. There is an excellent review on positive and negative nonlinear effects in asymmetric induction.124b... 

The asymmetric 1,3-dipolar cycloaddition of nitrones (515), possessing an electron-withdrawing group, to allylic alcohols was achieved by using diisopropyl (/ ,/ )-tartrate [(R,R-DIPT)] as a chiral auxiliary. The isoxazolidines (516) and... 

The flask was filled with activated powdered 4 A molecular sieves (500 mg), dry dichloromethane (40 mL) and L-(+)-diisopropyl tartrate (400 mg). 

The allyl boronate esters (R,R)- and (S,S)-1 are prepared by reaction of allylboronic acid, CH2=CHCH2B(OH)2 with l- and D-diisopropyl tartrate.1... 

IS, 2/ )-l-Cyclohexyl-2-methyl-3-buten-l-ol [Representative Procedure for Additions of ( )-Crotyl Diisopropyl Tartrate Boronate to Aldehydes]. ... 

The synthesis in Scheme 13.41 features use of an enantioselective allylboronate reagent derived from diisopropyl tartrate. The stereochemistry at the C-2 methyl group is influenced by the C-5 hydroxyl group, with 3 1 stereoselectivity for the desired stereoisomer. 

The real breakthrough in the field of enantioselective epoxidation was reached by Sharpless and Katsuki with the development of the catalytic system consisting of titanium tetraisopropoxide and optically active diethyl- or diisopropyl tartrate (DET or DIPT) and water-free TBHP as oxygen donor (Scheme This milestone in synthetic organic... 

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