2-Ethoxy-l,3-dithiolane

Aromatics containing electron releasing groups such as phenols, dim ethyl am in oben 2en e and indole are formylated by 2-ethoxy-l,3-dithiolane in the presence of boron trifluoroetherate, followed by hydrolysis (114). The preformed dithiolanium tetrafluoroborate also undergoes Friedel-Crafts reaction with aromatics such as dim ethyl am in oben 2en e and indole (115), and was used to generate dithiolanium derivatives (formyl precursors) from the enoltrimethylsilyl ether derivatives (116). 

Chloro-l,3-dithiane (797) has been employed as a formyl cation equivalent . The morpholine enamines of a variety of aldehydes and ketones were shown to react with this dithiane to produce the a-(l,3-dithan-2-yl) aldehydes and ketones (798) in good yield (Scheme 186) (77TL2077). In direct analogy with this work, the reaction of enol silyl ethers with 2-ethoxy-l,3-dithiolane in the presence of zinc chloride has been reported to afford half-protected 1,3-dicarbonyl compounds (81TL3243). 

Protected 1 -dicarbonyl compounds.5 Use of ZnCl2 as catalyst promotes the reaction of enol silyl ethers with 2-ethoxy-l,3-dithiolane (1) to give the protected derivative (2) of 1,3-dicarbonyl compounds. 

It was shown (78JFC(12)193) that the product of the reaction of perfhioro-2-methylpent-2-ene with potassium ethyldithiocarbamate in dimethylformamide is 5,5-bis(trifhioromethyl)-5-(tetrafluoroethylidene)-2-fhioro-2-ethoxy-l,3-dithiolane. Analogously, the reaction of 1,1,1-trifluoro-methyl-2-bromoprop-2-ene with thiourea and its N-substituted derivatives yields 5-trifhioromethyl-2-thione-thiazolidines 57 (92JFC(58)365). 

Die Herstellung der Alkalimctalldithiolate konnte einfacher erfolgen. Die Umesterung von 2-Ethoxy-l,3-dithiolan mit Desoxyribonucleosiden dient dem Schutz der 5 -Hydroxy-Gruppe298. 

Bis-[ethylthio -methoxy-methan Bis-[ethylthio]-ethoxy-methan Methoxy-methylthio-phenylthio-methan 2-Methoxy-l, 3-dithiolan 2-Methoxy-1,3-dithian 2-Isopropyloxy-l, 3-dithian... 

In Kiyooka s approach to acetate aldols by use of a stoichiometric amount of 3f, the enantiomeric excess obtained in the reaction with silyl ketene acetals derived from a-unsubstituted acetates was much lower (ca 10-20 %) than that obtained in the reaction with l-ethoxy-2-methyl-l-(trimethylsiloxy)-l-propene (> 98 % ee). Introduction of an removable substituent, e.g., a methylthio or bromo substituent, after aldol reaction at the a-position of chiral esters, resolved this problem [43e], Asymmetric synthesis of dithiolane aldols was achieved in good yield by using the silyl ketene acetal derived from l,3-dithiolane-2-carboxylate in the 3f-promoted aldol reaction, and desulfurization of the dithiolane aldols resulted in production of the acetate aldols in high enantiomeric purity (Eq. 56). 

The unsubstituted l,3-dithiole-2-thione (245) can be accessed, however, by the reaction of dimethyl acetylenedicarboxylate with l,3-dithiolane-2-thione (Scheme 50) <74JOC2456>, from the reaction of sodium acetylide with carbon disulfide and elemental sulfur <64CB1298>, or by a two-step synthesis from the 1,2-dichloroethyl ethylether (246) and potassium trithiocarbonate. The intermediary 4-ethoxy-l,3-dithiolone-2-thione (247) affords, upon reaction with p-toluene sulfonic acid with concomitant loss of ethanol, the unsubstituted derivative (245) <76CC920>. 

From, 2-Dithiolans Type C). The general synthesis of isothiazoles from 1,2-dithiolans (see Vol. 2, p. 563 Vol. 3, p. 543) by reaction with ammonia or amines continues to be exploited. 3-Ethoxy-l,2-dithiolium salts (1) are cleaved by primary amines to the linear thioesters (2), which are in turn convertible into... 

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