Stereochemical studies. VI. Asymmetric selection via elimination. Pyrolyses of optically active sulfoxides to optically active olefins

Goldberg, Stanley I.; Sahli, Muhammad S.

doi:10.1021/jo01282a003

Cited by 33 publications

(14 citation statements)

References 1 publication

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“…Found: 286.1022. 8a: ir (CC14) 1730; NMR (CC14) 4.13 (2 H, q, J = 7 Hz), 2.98 (1 H, d of d, J = 8.0, 7.5 Hz), 2.06 (3 H, s), 1.0-2.0 (17 H, m), 0.7-1.0 (3 H, unresolved t); mass spectrum (m/e, %) 248 (5), 247 (13), 246 (70), 201 (9), 200 (52), 199 (22), 174 (15), 173 (100), 172 (15), 157 (47), 134 (40), 88 (19). Caled for C13H2602S: 246.1653.…”

Section: Methodsmentioning

confidence: 99%

New synthetic reactions. Sulfenylations and dehydrosulfenylations of esters and ketones

Trost¹,

Salzmann²,

Hiroi³

1976

J. Am. Chem. Soc.

503

148

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Quenching the enolates of esters and ketones with dimethyl disulfide or diphenyl disulfide produces the corresponding a-sulfenylated products. The regio-and chemospecificity of these reactions are defined. Oxidation to the sulfoxide followed by thermolysis leads smoothly to the @unsaturated systems. Temperatures for the elimination of the phenyl sulfoxides are normally around 50 O C , whereas those for the methyl sulfoxides are normally around 110 O C . In both cases, the presence of the carbonyl group significantly facilitates the elimination. Dipole-dipole effects account, in part, for this effect and rationalize the regioselectivity observed in cyclic cases. In some cases, the use of sulfenic acid traps, amines or trimethyl phosphite, is required for good yields. The synthesis of two bee pheromones demonstrates the utility of this approach for introduction of unsaturation. Conditions for mono-vs. disulfenylation are discussed. Use of the latter to effect conversion of an active methylene group into a carbonyl group is illustrated.

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Section: Methodsmentioning

confidence: 99%

New synthetic reactions. Sulfenylations and dehydrosulfenylations of esters and ketones

Trost¹,

Salzmann²,

Hiroi³

1976

J. Am. Chem. Soc.

503

148

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“…276 The formation of C=C bonds by thermolysis of sulfoxides was also used in more sophisticated synthetic sequences. For example, this reaction served as a stage in the construction of brefeldin A (130) 181,183 and in the synthesis of hirsutene 207 (in the latter case, thermolysis was carried out in an alkaline medium according to a procedure reported previously 279 ). Other examples will be considered below.…”

Section: Formation Of C=c Bonds By Thermolysis Of Sulfoxidesmentioning

confidence: 99%

Sulfones and sulfoxides in the total synthesis of biologically active natural compounds

Prilezhaeva¹

2000

Russ. Chem. Rev.

185

103

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A graphical treatment of the tone reproduction problem in television systems satisfactorily answered by extensive experimental work, using the techniques of subjective appraisal which have been increasingly developed in recent years. Direct comparison of a reproduction and an original, with all the parameters of the system accurately known, calls, of course, for a considerable experimental effort. Such limited observations as have been made, however, suggest that the shape of the curves at least gives a good impression of the relative effects of viewing cathode-ray tubes with different values of A, and operating under, different conditions. It is not intended to draw any conclusions or express any as to what form of reproduction characteristic is most desirable. There can, however, be little doubt that there are instances where faithful reproduction is not desirable -where, in fact, the television system can improve on the eye and convey the maximum of information or enhance the asthetic value of a scene by emphasizing certain luminosity differences at the expense of others. To a large extent the value of such distortions must be a matter of personal preference.What constitutes the most desirable form of characteristic is, again, a question which calls for large-scale experiment on a subjective basis; factors such as signal-to-noise ratio and the effect of the characteristic on apparent definition have to be taken into account.Reference may be made in passing to the results of Jones's investigation into the preferences of a large number of observers in the matter of photographic prints.Q) This investigation tends to show that preferred prints are those in which the gradient of the logL,/logL, curve is approximately unity for the medium tones, and that a greater fall in the gradient is acceptable towards black. It would be unwise to assume, however, that the results obtained are necessarily applicable to television practice, where the form of the transfer characteristics and the viewing conditions are different. One general principle which does not seem to be in dispute is that, whereas a considerable tolerance exists when the reproduction is in monochrome, colour calls for a much closer approach to fidelity in luminosity reproduction.Large-area luminance range in modern aluminized cathoderay tubes, in the absence of external light, appears to offer little scope for worth-while improvement. It is worth noting, however, that the importance of good detail luminance range in determining the subjective quality of television pictures has been stressed by Law@) and other writers.Assuming that an optimum characteristic, or range of characteristics, can be defined, practical realization of the optimum raises a number of issues, e.g. the relative contributions of the transmitting and receiving apparatus to the overall result, and whether the desired objective can best be arrived at by selection of the camera or cathode-ray tube characteristic or by suitable circuit design.It is hoped that the present communication may help...

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“…31 The same microorganism was also reported to perform stereoselective oxidation of methyl 2-naphthyl sulfide (5) and to give small quantities of the corresponding sulfone from each substrate. These observations were followed by a brief abstract reporting the "sulfoxidation" of the antitubercular agent 6 by Septomyxa affinis38 and later by the first systematic study of the fungal oxidation of a series of unsymmetrical substituted thioethers, carried out in the laboratories of Professor H. B. Henbest. 39,40 The first indication that fungal cultures were capable of oxidizing thioethers to sulfoxides was provided by the observation that the addition of biotin (1) to the…”

Section: Enantioselectlve Enzymic Oxidation Of Sulfidesmentioning

confidence: 99%

Chiral sulfoxidation by biotransformation of organic sulfides

Holland¹

1988

Chem. Rev.

266

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Stereochemical studies. VI. Asymmetric selection via elimination. Pyrolyses of optically active sulfoxides to optically active olefins

Cited by 33 publications

References 1 publication

New synthetic reactions. Sulfenylations and dehydrosulfenylations of esters and ketones

New synthetic reactions. Sulfenylations and dehydrosulfenylations of esters and ketones

Sulfones and sulfoxides in the total synthesis of biologically active natural compounds

Chiral sulfoxidation by biotransformation of organic sulfides

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