Stork reagent

Stork reagent) 1,3-dithiane cleavage, 328-329 Iodoalkanes. See Haloalkanes Iodoetherification, 272, 326 Iodolactones. See Halolactones Ion-exchange resins. See Benzene, ethenyl- ... 

Stilbenes synthesis by Heck coupling, 43 Stille coupling aryl triflate + organylstannane, 42 Stobbe condensation, 58-59 Stork reagent, 328-329 Strain, steric. See Steric strain Strecker s synthesis of a-amino acids, 50, 301 L-Streptose synthesis, 267 Styrene. See Benzene, ethenyl-Succinic acid. See Butanedioic acid Succinimide. See 2,5-Pyrrolidinedione Sugars. See Monosaccharides Oligosaccharides inexpensive derivs. pr. (table), 263-264 Sulfafurazole, 307 Sulfamethoxazole, 308 Sulfenic acids, esters ... 

In the post-World War II years, synthesis attained a different level of sophistication partly as a result of the confluence of five stimuli (1) the formulation of detailed electronic mechanisms for the fundamental organic reactions, (2) the introduction of conformational analysis of organic structures and transition states based on stereochemical principles, (3) the development of spectroscopic and other physical methods for structural analysis, (4) the use of chromatographic methods of analysis and separation, and (5) the discovery and application of new selective chemical reagents. As a result, the period 1945 to 1960 encompassed the synthesis of such complex molecules as vitamin A (O. Isler, 1949), cortisone (R. Woodward, R. Robinson, 1951), strychnine (R. Woodward, 1954), cedrol (G. Stork, 1955), morphine (M. Gates, 1956), reserpine (R. Woodward, 1956), penicillin V (J. Sheehan, 1957), colchicine (A. Eschenmoser, 1959), and chlorophyll (R. Woodward, 1960) (page 5). ... 

Among other methods for the preparation of alkylated ketones are (1) the Stork enamine reaction (12-18), (2) the acetoacetic ester synthesis (10-104), (3) alkylation of p-keto sulfones or sulfoxides (10-104), (4) acylation of CH3SOCH2 followed by reductive cleavage (10-119), (5) treatment of a-halo ketones with lithium dialkyl-copper reagents (10-94), and (6) treatment of a-halo ketones with trialkylboranes (10-109). 

The enamine (16) is the best reagent for synthon (14) this was one of Stork s original enamine syntheses,... 

Oshima has demonstrated that the Schwartz reagent Cp2Zr(H)Cl can act as an excellent replacement for Bu3SnH for Ueno-Stork cyclizations (Scheme 4) [17]. 

Although the majority of sulfides used as precursors to organolithiums have been thioacetals or sulfides bearing other a-substituents, the usefulness even of simple phenylsulfides related to 56 was demonstrated in the synthesis of dihydroerythronolide A by Stork,74 which used a sulfide intermediate 59 in the conversion of an alcohol to a Grignard reagent. 

Michael additions of organotitanium or zirconium reagents remain to be explored systematically. Recently, Stork described an interesting stereoselective intramolecular Michael addition in which zirconium enolates appear to be involved113). In another Michael type process, methyltitanium triisopropoxide 6 was added enantioselectively to a chiral a, p-unsaturated sulfoxide, but CH3MgCl was more efficient114). 

In order to analyse the origin of regioselectivity in the lithiation of enamines in hydrocarbon solvents using alkyl lithium reagents, Stork and coworkers54 carried out a theoretical study at the 3-21G level of the lithiation of various vinylamines. 

Enamines have been recognized in organic chemistry as useful synthetic reagents since the early reports from Stork s laboratory1. At almost the same time similar chemical moieties were being implicated in biochemical systems. Because of their intrinsic instability in water, the biochemical enamines exist primarily as intermediates, although, some well-known coenzymes that participate in oxidation-reduction reactions also incorporate enamine structures in one of their oxidation states. The electronic structure of enamines involves two extreme resonance contributions as shown in equation 1. 

The Stork-Zhao method using [bis(trifluoroacetoxy)iodo]benzene has been widely adopted and is Likely to be the method of choice for the hydrolysis of 5,5-acetals. As little as 1.5 equivalents of the reagent will suffice and the reactions are usually complete in less than 10 minutes at room temperature. If the... 

Synthesis of aldehydes and ketones. This substance can function as a protected cyanohydrin of formaldehyde in an extension of Stork and Maldonado s synthesis of ketones from aldehydes, RCHO —> RCOR, by way of cyanohydrins (4, 300-301). Thus the anion of 1, generated with LDA, does not undergo self-condensation, but can be alkylated the product on hydrolysis gives the homologous aldehyde of the alkyl halide. Thus the reagent serves as the latent anion of formaldehyde, HC=0. An example is shown in equation (I). 

A most successful derivative, 2-trimethylsilyl-l-propcnc-3-one, has been developed and is a must in the stoek of reagents of any organic synthesis laboratoiy. See G. Stork and B. Ganem, J. Am. Chem. Soc., 95, 6152 (1973). For a convenient preparation see R. K. Boeekman, Jr., D. M. Blum, B. Ganem, and N. Halvey, Org. Synth., 58, 152 (1978). Fora review on the Robinson cyclization reaction see, among other contributions, R. E. Gawley, Synthesis, 777 (1976). 

The mechanism of the benzoin condensation, as depicted in Scheme 1, suggested that anions derived from a protected aldehyde cyanohydrin should function as nucleophilic acylating reagents. The use of protected cyanohydrins as carbanion equivalents has been studied by Stork and by Hunig and has found wide applicability in chemical synthesis. Such species may serve as either acyl anion equivalents or homoenolate anions. ... 

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