Alkylation, phase transfer

Perbenzoic acid, m-chloro- [Benzenecar-boperoxoic acid, 3-chloro-J, 55, 88 PHASE TRANSFER ALKYLATION, 55, 91 PHASE TRANSFER CATALYSIS, 55, 96 Phenol, thio- [Benzenethiol], 55, 122 Phenol, 2,4,6 tnbromo-, 55, 20 m-Phcnylenediamine [1,3 Benzenediamine], p-bromination of, 55, 23 Phosphine, phenyl-, bis(3-dimethylamino-... 

K. Manabe, Asymmetric Phase-Transfer Alkylation Catalyzed by a Chiral Quaternary Phosphonium Salt with a Multiple Hydrogen-Bonding Site , Tetrahedron Lett. 1998, 39, 5807-5810. 

K. Manabe, Synthesis of Nobel Chiral Quaternary Phosphonium Salts with a Multiple Hydrogen-Bonding Site, and Their Application to Asymmetric Phase-Transfer Alkylation , Tetrahedron 1998, 54, 14465-14476. 

J. J. Eddine, M. Cherqaoui, Chiral Quaternary Benzo-phenone Hydrazonium Salt Derivatives Efficient Chiral Catalysts for the Enantioselective Phase-Transfer Alkylation of Imines. Application to Synthesis of Chiral Primary Amines , Tetrahedron Asymmetry 1995, 6, 1225-1228. 

Modifications in the benzyl portion of the molecule are significant. The nitro group in the benzyl portion of the molecule apparently increases the local polarity of the transition state. The influence on the chemical and enantiomeric yield of variations in the benzyl portion of the quininium salt was dramatically confirmed recently by the work of Dolling and coworkers on the phase-transfer alkylation of a hydrindanone (83). 

C. Lemaire, S. Gillet, S. Guillouet, A. Plenevaux, J. Aerts, A. Luxen, Highly enantioselective synthesis of no-carrier-added 6-[ F]fluoro-L-DOPA by chiral phase-transfer alkylation, Eur. J. Org. Chem. 13 (2004) 2899-2904. 

Phase-transfer alkylation has been utilized in the preparation of 1-arylcyclobutanecarbonitriles starting from arylacetonitriles and 1,3-dihalopropanes.10... 

Pentynoic acid, 5-hydroxy-, 56, 51 2-Pcntynoic acid, methyl ester 55, 76 Peptides, 56, 88 Peracetic acid, 55, 87, 88 Perbenzoic acid, m-chloro-, 55, 88 Perbenzoic acid, 3-chloro-, 56, 1 Peroxydisulfunc acid ([(HO)S-(0)2 ] 2 Ot), diammomum salt, 56, 69 PHASE TRANSFER ALKYLATION, 55,... 

The results reported in this section are in agreement with the general behavior of intermolecular phase-transfer alkylations. The best yields are obtained when five- and six-membered rings are prepared. 

Further examples of alkylation of imidazole derivatives were recently reported by Galous et a/.145 The nature and importance of significant factors in phase transfer alkylation of pyrazole was studied by Elguero et al.146 Their conclusions are equivalent to those of Dehmlow and Lissel.147 The optimization method used by Elguero et al. (several parameters at a time) is different from the conventional procedure (one parameter at a time) and will probably find applications in the future for optimization of organic syntheses. 

Mathias and Burkett149 have also obtained two isomers in the phase-transfer alkylation of benzimidazoles (86), using an 18-crown-6 catalyst. 

The solubility of quaternary ammonium salts in the organic phase can profoundly affect the course of any phase transfer alkylation reaction, and the organic solubility of these quaternary ammonium salts is strongly dependent on the counterion. The estimated order of organic solubility of quaternary ammonium salts is5a ... 

Asymmetric induction has also been evaluated in the reaction of a-aryl substituted ketones, esters, and lactones (43). The potential of the method is demonstrated by the synthesis of some naturally occurring or nonnaturally occuring chiral compounds (Scheme 15). Similarly, asymmetric synthesis of ( — )-physostigmine, a clinically useful anticholinesterase agent, is accomplished by using phase-transfer alkylation of... 

In 1997 the Corey [1] and Lygo [2] groups disclosed the use of N-(anthracenyl)methyl-modified Cinchona alkaloids (e.g., 1) as catalysts in phase transfer alkylations, which afforded remarkable enantiomeric excesses of up to 99%. During the ensuing years, these groups have expanded the scope and limitations of these catalysts, as summarized below. 

Phase transfer alkylation of cyanomethyl group of 10-cyanomethyl-9-fluoro-3(S)-methyl-7-oxo-2,3-dihydro-7H-pyrido[l,2,3-de][l,4]oxazine-6-carboxylic acid with 1,2-dibromoethane in the presence of (PhCH2)Et3NBr... 

In the Park-Jew group s systematic investigation, two types of catalyst - the 1,3-phenyl- and 2,7-naphthyl-based dimeric ammonium salts - were selected as an efficient skeleton of chiral PTCs for the catalytic asymmetric phase-transfer alkylation... 

Having optimized the catalytic enantioselective phase-transfer alkylation system, the group explored the scope and limitations. A variety of electrophiles were reacted with the benzophenone imine glycine tert-butyl ester 1 catalyzed by 5 mol% of the selected chiral dimeric PTCs, benzene-linked-l,3-dimeric PTC 37, 2 -F-benzene-linked-1,3-dimeric PTC 41, and naphthalene-linked-2,7-dimeric PTC 39, at reaction temperatures of 0°C or — 20 °C (Scheme 4.8). 

Table 5.2 Catalytic enantioselective phase-transfer alkylation of glycine derivative 2 catalyzed by (S)-16Aa, (S)-16Ab, (S)-16Ba, and (S)-16Bb.

Table 5.3 Catalytic enantioselective phase-transfer alkylation of glycine derivative 2.

Table 5.5 Asymmetric phase-transfer alkylation of glycine amide Schiff base 22. 

Table 5.6 Asymmetric phase-transfer alkylation of protected glycine weinreb amides 23.

The vast synthetic utility of the asymmetric phase-transfer alkylation of glycine Schiff base 2 has been realized by its successful application to the synthesis of various useful amino acid derivatives and natural products. 

Table 5.7 Catalytic enantioselective synthesis of a,a-dialkyl-a-amino acids by phase-transfer alkylation.

Asymmetric phase-transfer catalysis with (S,S)-lg can be successfully extended to the stereoselective N-terminal alkylation of Gly-Ala-Phe derivative 61 (i.e., the asymmetric synthesis of tripeptides), where (S,S)-lg turned out to be a matched catalyst in the benzylation of DL-61, leading to the almost exclusive formation of DDL-62. This tendency for stereochemical communication was consistent in the phase-transfer alkylation of DDL-63, and the corresponding protected tetrapeptide DDDL-64 was obtained in 90% yield with excellent stereochemical control (94% de) (Scheme 5.30) [31]. 

Scheme 6.2 Catalytic asymmetric phase-transfer alkylation of various electrophiles.

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