A simple method of dethioacetalization

Stork, Gilbert; Zhao, Kang

doi:10.1016/s0040-4039(00)95181-5

Cited by 324 publications

(192 citation statements)

References 3 publications

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“…Moreover, hydrolysis of dithioacetals (17,18) with N-bromosuccinimide (NBS) 17) in aqueous 2-butanone gave the original ketones in good yields, while hydrolysis with methyl iodide, 18,19) phenyl iodine(III)bis(trifluoroacetate), 20) and Dess-Martin periodate 21) did not give good results (Table 3). We attempted to use 5-dodecyl-1,3-dithiane (19), which can be easily prepared from 2a and paraformaldehyde in the presence of p-toluenesulfonic acid in refluxed benzene, as a precursor of a carbonyl anion equivalent.…”

Section: Resultsmentioning

confidence: 99%

“…First, the proton at the C-2 position of 19 was abstracted with n-butyllithium to afford the odorless 1,3-dithiane anion. The reaction of the anion with n-dodecyl iodide gave trans-2,5-didodecyl-1,3-dithiane (20) in excellent yield. 22) Deprotonation of 2-substituted 5-dodecyl-1,3-dithianes (21, 22) and successive alkylation with n-dodecyl iodide yielded trans-2,5-didodecyl-1,3-dithiane derivatives (23,24), of which the yield was dependent on the bulkiness of the substituent at the C-2 position (Table 4).…”

Section: Resultsmentioning

confidence: 99%

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Preparation and Application of Odorless 1,3-Propanedithiol Reagents

Matoba

Kajimoto

Nishide

et al. 2006

CHEMICAL & PHARMACEUTICAL BULLETIN

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We have reported the preparation and application of odorless organosulfur reagents that can be used in place of ethanethiol, benzenethiol, phenylmethanethiol, and dimethyl sulfide in organic synthesis. [1][2][3][4][5] The strategy for reducing malodorousness is based on the increase in their molecular weights to raise boiling points and suppress volatilities. For example, dodecanethiol is completely odorless although decanethiol still smells faintly and ethanethiol, as is well known, creates a stench.1,3-Propanedithiol (1) as well as the other organosulfuric reagents mentioned above is an indispensable chemical especially in the protection of carbonyl groups, reduction of carbonyl groups to methylene via dithioacetal, and reduction of azides. Polymer-supported 1,3-dithiol [6][7][8] and ketene dithioacetal derivatives [9][10][11] were already reported to be odorless 1,3-dithiols, although the preparation of these reagents still requires odorous chemicals such as carbon disulfide and thioacetate. We here report a useful procedure in which neither odorous reagents nor a malodorous work-up are required to prepare odorless 1,3-propanedithiol and 1,3-dithiane derivatives with a long alkyl chain at the C-2 position, and their reactivity in several organic reactions as a part of our study on odorless organosulfuric reagents. Results and DiscussionIn spite of being a known compound, 2-dodecyl-1,3-propanedithiol (2a) was not prepared by the method reported in the literature accompanied by the generation of thioacetate 12,13) but by modifying Shon et al. 's method 14) to avoid generating malodorous odors during the reaction. The reaction of dodecyl bromide and diethyl malonate in the presence of sodium ethoxide giving diethyl 2-dodecylmalonate (3a) was followed by reduction with lithium aluminum hydride to afford 2-dodecyl-1,3-propanediol (4a). Thus the 1,3-diols (4a) were derived to give mesylate (5a), which was treated with thiourea and successively hydrolyzed with sodium hydroxide. The obtained substance must be reduced once with sodium borohydride to afford 2a in pure form due to the formation of disulfides (6a) by air oxidation during hydrolysis. 2-Decyl-1,3-propanedithiol (2b) was prepared in the same way from 3b via 4b, and 5b (Chart 1). As expected, 2a that was reported to form chelates with Au or 99m Tc was not malodorous, 14,15) while 2b smelled faintly. Next, the reactivity of 2a in several organic reactions was compared with that of 1.In general, reactions with 1,3-propanedithiol (1) proceed much faster than those with alkane thiols in the reaction requiring two equivalents of mercapto groups, since intramolecular nucleophilic attack by the second mercapto group of 1 causes less decrease in the activated entropy in the transition state than the corresponding intermolecular reactions. This could explain why the reduction of azides or dithioacetalization of carbonyl groups proceed more quickly when using 1 than when using alkane thiols. Thus diphenylmethyl azide (7) 16) and p-bromophenyl azide (8) were respecti...

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Preparation and Application of Odorless 1,3-Propanedithiol Reagents

Matoba

Kajimoto

Nishide

et al. 2006

CHEMICAL & PHARMACEUTICAL BULLETIN

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“…With this goal in mind, treatment of (Ϫ)-31 in MeOH with PhI(O 2 CCF 3 ) 2 , Stork's hypervalent iodide protocol (46), converted the dithiane to the corresponding dimethyl ketal (93%). Ley oxidation (47), followed by Pinnick oxidation (48,49) and immediate treatment with diazomethane, furnished the desired methyl ester (ϩ)-32 in modest overall yield (46%, three steps).…”

Section: Union Of the Northern And Southern Hemispheres Of (؉)-13-deomentioning

confidence: 99%

A unified approach to the tedanolides: Total synthesis of (+)-13-deoxytedanolide

Smith

Adams

Barbosa

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

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A unified approach for the construction of the potent marine antitumor agents (؉)-tedanolide (1) and (؉)-13-deoxytedanolide (2) is described. Highlights of the synthetic strategy include the development of a versatile bifunctional dithiane-vinyl iodide linchpin, the unorthodox use of the Evans-Tishchenko reaction, and a late-stage high-risk stereocontrolled introduction of the C(18,19) epoxide to achieve a total synthesis of (؉)-13-deoxytedanolide (2).

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“…166 The deprotection using PIFA can also be performed using an alcohol as solvent, directly delivering an acetal. 374 This protocol has been used in studies toward brevetoxin A, using MeOH as solvent (Scheme 74).…”

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confidence: 99%