Ethylene dithioacetals

Ethylene dithioacetals and diethyl dithioacetals have been investigated for a number of monosaccharides. The c.d. spectra show one, or two, c.d. band(s) of low intensity between 235 and 250 nm, and a third band of low intensity that peaks below 220 nm. These workers found no overall relationship between the configurational pattern of the monosaccharide and the sign of these bands. However, there does appear to be a correlation between the configurations of C-2, C-3 and C-4 and the sign of the c.d. band that peaks below 220 nm. 

Ethylene dithioacetals of benzophenone and its 4-fluoro-, 4-bromo-, 4,4 -difluoro-, 4,4 -dichlo-ro-, and 3,5-dimethyl-substituted analogs react with sulfuryl chloride or sttlfuryl chloride fluoride in hydrogen fluoride/ pyridine at — 78 C to room temperature to give the corresponding geminal difluorides in 85-90% yield. The reaction is, however, not applicable to dialkyl or alkyl aryl ketones as they undergo chlorination under these conditions.73... 

In related work,2123 2-amino-2-deoxy-D-glucose ethylene dithioacetal was deaminated at different pH values. In a system buffered at pH 5, three main products were isolated after the mixture... 

The peak of the molecular ion is, surprisingly, absent from the mass spectra of fully acetylated ethylene dithioacetals.41 Their fragmentation consists principally of elimination of CHaCOiH, CHaCOj-, CHsCO, and ketene in various combinations. The most intense peaks of the spectra are those at m/e 43 (CH.CO ), 45 (CHsS ), 01 (EtS ), and Xi (m/e 105) ... 

Fully acetylated diethyl dithioacetals are to be preferred to ethylene dithioacetals for analytical applications, as the mass spectra of the latter do not contain the peak of the molecular ion, and provide no information additional to that which can be drawn from the spectra of the former. 

Dimethyl phosphite has been added to glycosulose derivatives (for example, 218) as a means of preparing C-phosphono sugars.474 Methyl 2,3,6-tri-0-benzoyl-a-D-n 6o-hexopyranosid-4-ulose reacts with 1,2-ethanedithiol to form the corresponding 4,4-ethylene dithioacetal.475... 

Dethioacetalization. Ethylene dithioacetals are cleaved to carbonyl compounds by nitronlum tetrafluoroborate in excellent yield. Other somewhat less effective reagents are N0 HS04 and NaNOa or NaNOj in TFA. 

Aldosulose derivatives having unprotected ketonic functions have been converted into similarly substituted ethylene dithioacetals by the action of 1,2-ethanedithiol in the presence of boron trifluoride. l,6-Anhydro-2,4-dideoxy-jS-D-glt/cero-hexopyranos-3-ulose70 (9)... 

At neutral pH, hydrolysis is extremely slow, but the reaction proceeds to completion with minimal interference from side reactions as an increase in the acidity of the medium not only accelerates the rate of hydrolysis but also introduces competing reactions and displaces the equilibrium towards the dithioacetal, the optimal conditions for the demercaptalation reaction are a compromise176 between the rate and the yield of the reaction. The identity of the thiol also influences the rate of mercury(II) chloride-catalyzed hydrolysis, diphenyl dithioacetals reacting30 very readily and ethylene dithioacetals slowly188,235 or not at all,72 the reverse of their relative rates of formation. 

Finally MacDonald and Fischer have prepared the free ajyZo-pento-dialdose (8) by the sulfone-degradation method. The diethyl dithioacetal of scyllo-inosose (12) was oxidized to the corresponding disulfone which, on treatment with ammonia, gave the dialdose (8). The structure was proved by converting the compound into the bis(ethylene dithioacetal) derivative, which was identical with that obtained from a /io-pentodialdose prepared by a previous method. ... 

D-fiflwco-Hexodialdose and n-manno-hexodialdose have been reported to give crystalline bis (diethyl dithioacetal) derivatives, by the addition of ethanethiol to the dialdose dissolved in cold concentrated hydrochloric acid. The difficultly soluble dithioacetal readily precipitated after a short time. Similarly, the crystalline bis (ethylene dithioacetal) of xylo-pento-dialdose was prepared. A liquid bis(diethyl acetal) of erj/tliro-tetrodialdose and of the isopropylidene acetal of n-i/ireo-tetrodialdose " have also been reported. 

Ethylene dithioacetal derivatives of cyclohexanone and substituted cyclohexanones are also reported to be rapidly and smoothly converted into 2,3-dihydro-1,4-benzodithiins by simple treatment with bromine in anhydrous chloroform at room temperature <91T4187>. 

Ethylenebis(l,3-dithiane), 223 Ethylene dithioacetals, 265 Ethylene dithiokctals, 30-31 Ethylene glycol, 125 Ethylene ketals, 262... 

---