Ketene dithioacetals synthesis

Matsuda et al. <1995H(41)2777> described an efficient synthesis of mesoionic [l,2,4]triazolo[4,3-A]pyridazines 390 and 391. The starting compound for the synthesis is the A-aminotriazole 389, which can be treated either with ethyl 2-chloro-3-ethoxyacrylate to yield 390 or with ketene dithioacetals to afford 391. The reactions proceed in good to high yield. 

The stereoselective intramolecular coupling of a ketene dithioacetal to an oxygen nucleophile to afford (10), was used as a key step in the total synthesis of (+)-nemorensic acid [229]. 

Mukaiyama reported the conjugate addition of a-dithioalkylcuprates to 2-enones (73-94% yields) for the synthesis of 1,4-diketones, and the reaction was exploited in a synthesis of(+)-dihydrojasmone [141]. Few reports on a-thioalkylcuprates have appeared since then. Cuprates formed from lithiated ketene dithioacetals and... 

Ketene dithioacetal 237, obtained from acetylacetone, can serve as the initial reactant for the synthesis of aminopyran 238, spiro-annulated with oxazolidine (00SC1269) (Scheme 91). 

The ketene dithioacetal method group has proved useful for the synthesis of a number of biologically interesting molecules <2000BML703, 2004EJM969>, including 5-cyanopyrimidine derivatives which are orally active inhibitors... 

The synthesis of substituted selenolo[2,3-. ]thiophenes via ketene dithioacetals was published by the same research group <20048451>. 

A practical synthesis of ketene dithioacetals of sugars was discovered by Horton and Wander.281,182 This reaction does not need to be emphasized here, as it has been discussed in this Series (see Ref. 7, and references cited therein). We only recall as an example that the... 

This reaction provides a synthesis of trans-calamene (7) from the ketene dithioacetal (5) of /-menthone. 

Ripoll and coworkers288 have reported the cleavage of silylated ketene dithioacetals under flash vacuum thermolysis (FVT) conditions20, which allowed the synthesis of propadienethione by combining this process along with the retro-Diels-Alder reaction (see Section III.F.5). Propadienethione was not isolated, but it underwent addition of the nucleophiles present in the reaction mixture288 (equation 65). 

A general method for the synthesis of 2-deoxyaldoses utilizes a reaction sequence involving the formation and subsequent reduction of ketene dithioacetal intermediates (Scheme 10). Reduction of ketene diethyl dithioacetal 12 with lithium aluminum hydride proceeds via the alkoxyaluminum hydride salt involving the 3-hydroxyl group. Several deoxy hexoses and pentoses were prepared by this method, and also their 2-deuterio analogues.45... 

The synthesis of substituted sclcnolo 2,3-/ ]thiophcncs 208 and selenolo [2,3-b selenophenes 209 via ketene dithioacetals has been published (Scheme 40) [55], The easy access to ketene dithioacetals via carbon disulfide cannot be applied to selenium since the strongly odorous carbon diselenide cannot be readily prepared. The authors [55] overcame this problem using sodium selenide for the synthesis of selenolo[2,3-/ thiophcncs 208, which could be synthesized from methylsulfanylthiophenes 206 and sodium selenide and/or from 5-methylsulfanylselenophenes 207 and thioglycolate. 

Cazes, B. Julia, S. Preparation and utilization of two C5 conjugated ketene dithioacetals as isoprene synthons. Synthesis of (-)-(E)-lanceol. Tetrahedron Lett. 1978, 4065—4068. 

The high diastereoselectivity attending the spirocyclisation of ketene dithioacetals provides an effective means for controlling the stereochemistry of a methyl substituent at the a-position on a 6-lactone ring,244 The method was applied to the synthesis of the polyether antibiotic Salinomycin [Scheme 2.120].242 Condensation of the methyl ketone 120 1 with the lithiated l,3-dithian-2-yl-phospho-nic acid diethyl ester 120.2 gave the ketene dithioacetal 1203 in 76% yield. After hydrolysis of the two benzoate ester groups, cyclisation of diol 120.4 was... 

Pyridone derivatives, synthesis using ketene dithioacetals 89-YGK413. 

The S-OT o-cyclization of amino-ketene dithioacetals such as 183 is also a viable method for the synthesis of sulfur-substituted oxazoles 184 (Scheme 51) <2002RJC1714>. 

Acyl anion equivalents. Benzotriazol-l-ylmethyl methyl sulfide can undergo consecutive C-alkylations. The products are readily hydrolyzed with acidic aqueous methanol to give ketones. A related process involving alkylation and sulfenylation followed by treatment with a Grignard reagent to eliminate benzotriazole completes the synthesis of ketene dithioacetals. ... 

Conjugate reduction. Ketene dithioacetals in which the C=C double bond is part of a conjugate system suffer reduction to give dithiane derivatives. The stereocontrol afforded by an Ar-complexed tricarbonylchromium moiety during reduction of a conjugated ester (also with transesterification) is a critical feature of a synthesis of mutisianthol. ... 

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