Meyers synthesis

Alkylation of Dihydro-1,3-Oxazine The Meyers Synthesis of Aldehydes, Ketones, and Carboxylic Acids... 

Sato Oguro Watanabe Sato Tetrahedron Lett. 1980, 21, 2869. For another method of convening RMgX to RCHO, see Meyers Comins Tetrahedron Lett. 1978,5179 Comins Meyers Synthesis 1978, 403 Amaratunga Frtchcl Tetrahedron Lett. 1983,24, 1143. 

This synthesis resolved one of the issues encountered in the Meyers synthesis, i. e. the epimerization of configurationally labile intermediates, since in this case the rotation around the biaryl axis is precluded by the presence of the bulky chromium tricarbonyl group. 

Figure 3.11 Structures of (a) [Sm2L6(MeOH)4] (HL = benzoic acid) and (b) [Pt2L6(H20)3] (HL = acetic acid) [RE, black O, grey C, white H, omitted]. (Redrawn from the CIF files of U.R Singh, R. Kumar and S. Upreti, Synthesis, structural, photophysical and thermal studies of benzoate bridged Sm(III) complexes, Journal of Molecular Structure, 831 (1-3), 97-105, 2007 [56] and D. Deiters and G. Meyer, Synthesis and crystal structure of praseodymium propionate trihydrate, Pr(CH3CH2C00)3(H20)3, Zeitschrift filr Anorganische und Allgemeine Chemie, 622 (2), 325-328, 1996 [57].)...

Meyer synthesis. Formation of aliphatic nitrites and nitro derivatives by the reaction of aliphatic halides with metal nitrites. 

Several examples exist wherein the chirality of the substrate serves to influence the degree of diastereoselectivity obtained on oxidation with racemic and nonracemic oxaziridines. These examples are different from those above, since an auxiliary whose sole purpose is to direct the stereoselectivity is not present. The majority of these examples rely on cyclic stereocontrol to direct the facial selectivity. For example, in Meyers synthesis of the AB-ring of aklavinone, oxidation of the thermodynamic enolate derived from 33 resulted in the production of tertiary a-hydroxy ketone 34 as a single diastereomer in modest yield.23 The stereoselectivity is rationalized by invoking a transition state wherein pseudo axial addition to... 

The Meyers synthesis of biaryls Preparation of biphenyl-2-carboxylic acid (543) [40)... 

Using other chiral 1,2-diols such as 1,2-diphenyl-1,2-ethanediol or 2,3-butanediol, the Lipshutz approach allows to rich very high diastereoselectivity [19]. Among reactions that have been used in the diastereoselective synthesis of unsymmetrical axially chiral biaryls, beside Ullmann and Lipshutz reactions, are the Suzuki-Miyaura and Meyers synthesis of biaryls. 

However, in the Suzuki-Miyaura reaction of relatively simple, enantiomerically pure, both naphthyl bromides and naphthylboronic acids gave diastereomeric mixtures, indicating rather low diastereoselectivity [21]. More important access to axially chiral biaryls is the Meyers approach in its diastereoselective version [22-25]. It was foimd that oxazolines, derived from readily available amino alcohol 585 [22], underwent the Meyers synthesis of biaryls giving the expected biaryls in high d.e. s [23-25]. Thus l-methoxynaphthyl-2-carboxamide (586) was activated with triethyloxonium tetrafluoroborate to 587, which reacted with 585 to give the oxazoline 588. The latter... 

Diastereoselective Meyers synthesis have been also efficiently employed at tn-ortho-substituted biphenyls [24], and various natural products, e.g. (-)-steganone. For instance, compound 592 was converted to the corresponding Grignard reagent 593, which subsequently reacted with chiral oxazoline 594 to afford the respective biphenyl 595, isolated after single recrystallization (EtOAc) as pure diastereomer in 65% yield [25], Scheme 9. 

The efficacy and the chiral leaving group-induced enantioselectivity in the Meyers synthesis of axially chiral biaryls of some selected examples are given in the Table 1. 

Table 1. The yields and enantioselectivity in the Meyers synthesis of biaryl 608 from oxazolines bearing the chiral leaving group [26]...

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