A-Sulfonyloxy ketones

Treatment of polymer-supported a-sulfonyloxy ketones with thioamides in the presence of potassium carbonate affords 1,3-thiazoles (Scheme 19).41... 

The reaction of bisnucleophiles with a-sulfonyloxy ketones bound to a resin results in the release of heterocycles 1,2-benzenedithiol gives 1,4-benzodithiins, 2-mercaptoethanol yields 1,4-oxathiins and 1,2-diols afford 1,4-dioxins <02JA5718>. 

Acetylene synthesis (2, 419-422). Wieland1 has extended the fragmentation of << /3-epoxyketones to give acetylenes to a new synthesis of acetylenes by the reaction of a-halo. or a-sulfonyloxy ketones with p-toluenesulfonylhydrazine. Thus reaction of either (la) or (lb) with p-toluenesulfonylhydrazine in the presence of potassium acetate in methylene chloride-acetic acid (4 days) gives the acetylene (2) in 50% yield. 

A one-pot procedure for the a-tosyloxylation of ketones by the reaction of ketones with mCPBA and TsOH H2O in the presence of catalytic amounts of NH4I and benzene in a mixture of MeCN and trifluo-roethanol (8 2) has been reported (Scheme 4.67) [110]. This method has some advantages, such as mild reaction conditions with a simple procedure and it is suitable for preparing not only a-tosyloxy ketones but also other a-sulfonyloxy ketones. It has been suggested that [hydroxyl(tosyloxy)iodo]benzene, generated by the reaction of iodide anion with mCPBA, benzene and TsOH, serves as the active species in this reaction [110]. 

More recently, worlc has been reported showing that silyl enol ethers of ketones, esters and lactones can be efficiently converted to a-sulfonyloxy carbonyl compounds on treatment with either [hydroxy(to-syloxy)iodo]benzene or [hydroxy(mesyloxy)iodo]benzene (equation 23). This method is similar to that used by the same workers to introduce the trifluoromethylsulfonyloxy group a to ketone carbonyl groups via their silyl enol ethers.While the major interest in these developments is the further func-tion zation of the a-position of carbonyl compounds the method clearly offers a route to a. -unsatu-rated species. 

An operationally simple procedure involving a variation of this reaction and relying on the use of a polymer-supported [hydroxy(sulfonyloxy)iodo]benzene with aromatic ketones or alcohols has also been published <2004S2673>. 

Fragmentation of appropriate bicyclic sulfonyloxy alcohols or ketones is a general route towards cy-cloalkene ketones or carboxylic acids. Thus, the hydroazulene alcohol (59 Scheme 22), precursor for the synthesis of daucene (60), jaeschkeana diol and others, has been synthesized by a one-pot reaction (fragmentation and isopropylation) of the hydroxy tosylate (57) with Pr Li. The fragmentation of (57) to give the ketone (58) as the primary product can be achieved by treatment with pyridine. 

An example of palladium-catalyzed furan synthesis utilizing allenes as starting materials was reported, in which 2,4-disubstituted-2,3-butadienoic acids and 1,2-propadienyl ketones were used and 2,4-disubstituted furans were produced. The reaction may proceed via a matched double oxypalladation-reductive elimination process <04CEJ2078>. In a similar cycloisomerization of substituted allenes to tri- and tetrasubstituted furans with regioselectivity, the allenes were produced in situ from acyloxy-, phosphatyloxy- and sulfonyloxy-substituted alkynylketones via a 1,2-migration of such substituents catalyzed by CuCl or AgBF <04AG(E)2280>. 

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