Ketones reactions with dithioacetals

Ketene dithioacetal 82 reacts with aromatic methyl ketones to generate thiopyranones. Further reaction with ethyl mercaptoacetate leads to the formation of thieno[3,2-f]pyranones in good yields (Scheme 18) <1997BML3101>. 

The stoichiometric equivalents of halofluorides have been recently applied to transform alkylene dithioacetals into gcm-difluorides.70-71 Dithioacetals such as 1,3-dithiolanes and 1,3-dithianes arc readily obtained from the corresponding carbonyl compounds by the reaction with ethane-1,2-dithiol or propane-1,3-dithiol in the presence of the complexes boron trifluoride-bis(acetic acid) or boron trifluoride-diethyl ether. Using a two-step procedure, a range of aldehydes and ketones can be converted into gem-difluorides under mild conditions. 

The second method consists in the reaction of 3-mercaptopropionic acid amides with various aldehydes and ketones (method B) this reaction proceeds via the formation of thiohemiacetal 143. Method B was modifed (in the case of p-chlorobenzaldehyde) by means of dithioacetal 144, which was isolated and then introduced into the reaction with the second mole of aldehyde (Scheme 49). 

Aldehydes may be prepared from the lower homolog or a ketone or ester by reaction with the anion of formaldehyde mono- or dithioacetal. The j6-hydroxythioacetal may be reduced with elimination of a hydroxyl group and phenylthiolate. The resulting enol ether or thioenol ether can be transformed into an aldehyde on acid hydrolysis or reaction with mercuric chloride [82],... 

In dithioacetals the proton geminal to the sulfur atoms can be abstracted at low temperature with bases such as Bu"Li. Lithium ion complexing bases such as DABCO, HMPA and TMEDA enhance the process. The resulting anion is a masked acyl carbanion, which enables an assortment of synthetic sequences to be realized via reaction with electrophiles. Thus, a dithioacetal derived from an aldehyde can be further functionalized at the aldehyde carbon with an alkyl halide, followed by thioacetal cleavage to produce a ketone. Dithiane carbanions allow the assemblage of polyfunctional systems in ways complementary to traditional synthetic routes. For instance, the p-hydtoxy ketone systems, conventionally obtained by an aldol process, can now be constructed from different sets of carbon groups. ... 

A substantial body of literature has been devoted to the study of condensation reactions of dithioacetals with aldehydes and ketones. Although phosphoric anhydride has been used as a catalyst for these... 

Looking carefully at the current literature we have learned that the ketene dithioacetal chemistry, widely used for one-carbon homologation of carbonyl compounds, has never been utilized for the construction of ulosonic acids [129]. Besides, ketene dithioacetals, readily available from ketones and aldehydes via the reaction with the ylides generated from substituted dithioacetals in the Peterson, Wittig or Homer-Emmons olefmation, have never been synthesized from lactones. 

Dithioacetals RCH(SPh)2 and vinylogues [i.e., RCH(SPh)CH=CHSPh] become carbanion equivalents [RCH2] when they are treated with Cp2Ti[P(OEt)j]2 and Mg. Thus, a subsequent reaction with nitriles furnishes ketones. Conjugated dienes and alkenylcyclopropanes are also obtained. ... 

Thioacetalization. In the reaction with 1,2-ethanedithiol, aldehydes and ketones are converted to dithioacetals very rapidly at room temperature (17 examples, 75-99% yield),... 

Ketene dithioacetals. This reagent (1) can be used for preparation of ketene dithioacctals by reaction with triphcnylphosphine or triethyl phosphite to form 2 or 5. I hc former reagent (2) can be used to form ketene dithioacctals (4) from aldehvalcs the hitler reagent (5) can be used with cither aldehydes or ketones. 

Oxodithioesters (123) reacts with methyl 4-bromocrotonate (124) to give the mixed dithioacetals (125), which immediately undergo an intramolecular aldol condensation to provide a practical synthesis of thiophenes (126) (Scheme 32) <88S556>. Similarly, reaction of 3-oxothioamides (127) with (124) gives thiophenes (128) (Equation (10)). Reaction of the chlorinated a, -unsaturated ketones (129) with ethyl thioglycolate followed by aldol condensation also provides thiophenes... 

Thiols react with aldehydes and ketones to give dithioacetals or dithioketals. 1,2-Dithiols react with aldehydes and ketones to give 1,3-dithiolane derivatives and 1,3-dithiol reactions to give 1,3-dithiane derivatives. 

Thiols react with aldehydes and ketones to give dithioacetals or dithioketals. 1,2-Dithiols react with aldehydes and ketones to give 1,3-dithiolane derivatives and 1,3-dithiol reactions to give 1,3-dithiane derivatives 34, 35, 36, 37, 38, 77, 78, 79, 80, 81. Primary amines react with aldehydes and ketones to give imi-nes. Secondary amines react with ketones and sometimes with aldehydes to give enamines 39, 40, 41, 42, 43, 44, 45, 46, 47, 61, 73, 84,89, 93. 

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