2,4-Disubstituted furans are prepared by treating 2,3-dibromo-1-phenylsulfonyl-1-propene (DBP, 2) with 1,3-diketones under basic conditions. The furan-forming step involves a deacetylation, and the selectivity of this process depends upon the steric demand of the R group. The substituent in position 4 is elaborated by reaction of sulfonyl carbanions with alkyl halides, acyl halides, and aldehydes. Oxidative or reductive desulfonylation produces the 2,4-disubstituted furans in 60-92% yield. This strategy has been used to prepare rabdoketone A (12) and the naturally occurring nematotoxic furoic acid 13.

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A convenient preparation of 2,3-dibromo-1-(phenylsulfonyl)-1-propene (DBP, 1) is available through the one-pot propargylation and oxidation of thiophenol to give the propargyl sulfone 11, which is isomerized and brominated in another one-pot reaction. The new preparation is significantly more scalable, as well as more convenient and robust than the prior art.

Propargyl xanthates undergo rearrangement to afford intermediary bis(alkylidene)dithiolanones which are trapped by Diels-Alder cycloaddition to yield dithiolones, representing three new carbocycle types such as (II), (VIII), and (X). The approach is not limited to scaffolds containing a rigid aryl backbone, but may also be applied to systems incorporating aliphatic and heteroaliphatic skeletons like propargyl xanthates (XI). Under similar conditions tetrahydrofuran, -pyran, pyrrolidine, and piperidine heterocyclic structures can be obtained. -(HARRINGTON, R. M.; WRIGHT, D.; ZARD*, S. Z.; Heterocycles 86 (2012) 2, 965-971, http://dx.doi.org/10.3987/com-12-s(n)98 ; Dep. Chem., CNRS, Ec. Polytech., F-91128 Palaiseau, Fr.; Eng.) -H. Hoennerscheid