Nucleophilic replacement reactions

J. Hill, L. Hough, and A. C. Richardson, Nucleophilic replacement reactions of sulphonates. I. The preparation of derivatives of 4,6-diamino-4,6-dideoxy-D-glucose and -D-galactose, Carbohydr. Res., 8 (1968) 7-18. 

Y. Ali and A. C. Richardson, Nucleophilic replacement reactions of sulphonates. III. The synthesis of derivatives of2,3,4,6-tetra-acetamido-2,3,4,6-tetradeoxy-D-galactose and-D-idose,/. Chem. Soc., Sect. C (1968) 1764-1769. 

It is often possible to predict the reactivity of a chlorosulfonyloxy group by a consideration of the steric and polar factors affecting the formation of the transition state,27-28 as indicated in Section 11,1 (see p. 227) for nucleophilic-replacement reactions of sulfonic esters of carbohydrate derivatives. Thus, it has been found that the presence of a vicinal, axial substituent or of a (3-trans-axial substituent on a pyranoid ring inhibits replacement of a chlorosulfonyloxy group also, a chlorosulfate group at C-2 has been observed to be deactivated to nucleophilic substitution by chloride ion. 

R. Khan and L. Hough, Nucleophilic replacement reactions of sulfonates. Part VII. Selective tosylation of methyl 2-benzainido-2-deoxy-a-D-gIucopyranoside and a synthesis of methyl... 

Properties of Benzo[b]thiophenes Containing a Halo Atom in a Side Chain, and Their Derived Crignard Reagents Side-chain halobenzo[6]thiophenes undergo most of the expected nucleophilic replacement reactions. Replacement by the cyanide... 

The main use of nitro-1,5-naphthyridines has been as precursors for 1,5-naphthyridinamines. However, the presence of a powerfully electron-withdrawing nitro group is often of use to activate adjacent leaving groups such as halogeno toward nucleophilic replacement reactions. 

Steric course at C-/J in nucleophilic / -replacement reactions catalyzed by PLP enzymes... 

Hill, J, Hough, L, Richardson, A C, Nucleophilic replacement reactions of sulphonates Part II. The synthesis of derivatives of 4,6-dithio-D-galactose and D-glucose, and their conversion into 4,6-D-xy/o-hexose, Carbohydr. Res., 8, 19-28, 1968. 

Tertiary amine trishydrofluorides are stable complexes, very convenient for the delivery of hydrogen fluoride. They can be distilled in vacuo, and are suitable reagents for the nucleophilic replacement reactions of chlorine by fluorine under mild homogeneous conditions. The reaction of COCl, with Et3N.3HF [680] in dry ethanenitrile at room temperature proceeds quantitatively according to ... 

Nucleophilic displacements. Ali and Richardson8 state that this solvent is far superior to DMF for nucleophilic replacement reactions of sulfonate esters in the carbohydrate field. Lower temperatures (80-100°) can be used and the reaction mixture remains almost colorless. 

The stereochemistry of the PLP-dependent elimination/substitution reactions involving the /3- and -y-carbons of amino acid substrates generally conforms to the trends observed among the PLP-dependent transamination and decarboxylation reactions at the a-carbon [Eq. (44)]. All of the enzymes so far studied that catalyze nucleophilic replacement reactions at the j8-carbon (five examples e.g., tryptophan synthase) and/or a,j3-elimination reactions (seven examples e.g., tryptophanase) involve retention of configuration at the jS-carbon (231) (Eq. (54)] ... 

A detailed study of the orientation and reactivity in the nucleophilic replacement reactions of aromatic polyhalo-compounds has been published . This involves study of the stability of the Wheland type intermediates (17, 18) where Nu is a nucleophile. The formation of meta... 

Richardson, A. C. Nucleophilic Replacement Reactions of Sulphonates. Part VI. A Summary of Steric and Polar Factors. Carbohydr. Res. 10, 395 (1969). 

Nucleophilic replacement reactions (by AcS, Ph CO S , MeS , and PhCHaS") with methyl 0-toluene-p-sulphonyl-L-lactate and sodium L-2-chloropropionate give 2-acylthio- and 2-alkylthio-D-propionic acids and esters. Extensive racemization accompanies the use of excess thio-acetate or thiobenzoate, due to further 5 2 replacement reactions, as observed for LiAlH4 reduction of L-(2-methylthio)propionic acid or its methyl ester. Diborane reduction gives optically pure L-(2-methylthio)-propanol, however. This work includes a new synthesis of ( + )-2-mercaptopropionic acid, though by known methods, and establishes the D configuration for this isomer. 

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