Eliel reagent

Organolithium reagents reaction with imidothioesters 114 reaction with isothiocyanates 42 reaction with non enethiolizable dithioesters 98 Orthotrithioesters 79 cleavage of 79 reaction with ketones 137 Oxathiane Eliel reagent 19 Oxaziridines as oxidising reagents 27 Oxiranes... 

Many studies have been directed toward the empirical development of synthetically effective reagents for asymmetric reductions. Criteria for an efficient asymmetric synthesis have been summarized by Eliel (12) as follows ... 

Horeau and co-workers (130) found that an ether solution containing four molar equivalents of (+ )-camphor added to one molar equivalent of LAH, followed by addition of A1C13, reduced 2-butanone or pinacolone. The reagent involved is presumably the same as that prepared by Eliel and Nasipuri (111), although the reaction leading to the formation of 111 is different (eq. [29]). The... 

Eliel s oxathiane auxiliary was used for stereoselective transformations and has been reviewed in part <2003H(60)1477>. As expected, reaction of the lithiated auxiliary with acetaldehyde gave the addition product with low stereoselectivity at the side-chain stereocenter <1997M201>. Better stereocontrol was observed, when methyl Grignard reagent was added to 2-acyl-l,3-oxathiane <2000JCCS63>. Reaction of 2-vinyl-l,3-oxathiane with 1,1-diphenylethene, mediated by TiCU, afforded dihydrothiopyrans in 82% yield, albeit with low enantioselectivity (Scheme 84) <2003T1859>. 

Lanthanide shift reagents A variety of these reagents are available commercially and they are generally quite stable and should not deteriorate on long storage in a dry state and in the absence of light. See G.R.Sullivan in Topics in Stereochemistry (Eliel and Allinger eds) J Wiley Sons Vol 10 287 1978, ... 

Eliel s oxathiane reagent, derived from (fl)-pulegone, is a valuable template for asymmetric syntheses. A large-scale preparation has appeared in Organic Syntheses [57]. 

The reaction of orthoesters with Grignard reagents provides a well known route to acetals and ketals U->-2). Eliel and Nader (1) have investigated the stereochemistry of this reaction and have concluded that it is governed by powerful stereoelectronic effects. 

This rationalization indicates that internal delivery of a hydride is not a requisite for the observed stereospecificity. Reduction of the oxonium ion with an external hydride reagent should also give equatorially oriented bicyclic ether only. Accordingly (112), reduction of tricyclic spiroketal 145 with sodium cyanoborohydride at pH =3-4 yields only the equatorial bicyclic ether alcohol (J47, CHO=CH2OH). Eliel and co-workers (113) have previously suggested that the orientation of the electron pairs of oxygen atoms influence the course of the reduction of 2-alkoxytetrahydropyran with lithium aluminium hydride-aluminium trichloride. 

Eliel, E. L. Nader, F. W. Conformational analysis. XX. The stereochemistry of reaction of Grignard reagents with ortho esters. Synthesis of 1,3-dioxanes with axial substituents at C-2.]. Am. Chem. Soc. 1970, 92, 584-590. 

Like the 1,3-dithianes, 1,3-oxathianes can be metallated with alkyllithium reagents and they hydrolyse about 10,000 times faster with protic acids. However, their value is diminished by the limited stability of the lithio derivatives and their inherent lack of symmetry which introduces the complications of diaster-eoisomerism. Eliel and co-workers have exploited the diastereoisomerism of... 

Eliel has extensively studied the 1,3-oxathiane systems (55) as a chiral auxiliary to control the addition of organometallics to ketones (Scheme 3). Following nucleophilic addition, cleavage of the oxathiane group generates chiral a-hydroxycarbonyl compounds (58). The wide variety of carbonyl substituents, as well as Grignard reagents, amenable to this process is illustrated in Table 14. The enantiomeric auxiliary is available, and affords alcohols of opposite chirality in equivalent yields. 

Eliel and co-workers investigated several acetals and ketals and found reduction in ether by mixed hydride to be a general reaction. Best yields are obtained when the ratio of LiAlH4 to AICI3 is 1 4 and the reagent is taken in 100% excess. Typical examples are ... 

Eliel and Fisk, who describe the Mannich condensation with the reagent to produce 5-methylfurfuryldimethylamine, state that the commercial material contains a stabilizer which can be removed by storage over solid KOHfor24 hrs., decantation, and storage over fresh KOH. 

G.R.SuUivan in Top Stereochem (Eliel Allinger Eds) J Wiley Sons Vol 10 287 1978, T.C.Morrill Ed. Lanthanide Shift Reagents Deerfield Beach Florida 1986, ISBN 0895731193.]... 

As noted (1, 132), an early procedure of Eliel and Doyle for the reduction of 4-t-butylcyclohexanone to cis-4-f-butylcyclohexanol used iridium trichloride supplied by Fisher. This reagent is no longer available and, in a newer procedure,1 iridium tetrachloride is used as catalyst in combination with trimethyl phosphite, which undergoes hydrolysis to phosphorous acid the actual reducing agent is probably... 

---