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(−)-(1R,2S,5R)-Menthyl (SS)-p-toluenesulfinate and its enantiomer are a common source for a chiral sulfoxide group in organic synthesis, by means of nucleophilic substitution. The replacement of the menthyloxy group, with complete inversion of configuration at the sulfur center of the chiral sulfoxide, allows the inclusion of this organic function into numerous substrates, with defined stereochemistry and high enantiomeric purity. Nine C3-substituted, enantiomerically pure, 2-sulfinylfurans were prepared by this synthetic methodology with moderate to high yields. These enantiopure C3-substituted 2-sulfinylfurans can be used as chiral dienes for [4+3] cycloaddition reactions and in other chemical transformations, in which π-facial selectivity should be induced in order to obtain enantioselective reactions.

The use of the p-tolylsulfinyl group as a chiral inductor in stereoselective [4+3] cycloaddition reactions has made possible the preparation of enantiopure polysubstituted 8-oxabicyclo[3.2.1]oct-6-en-3-one systems having up to five stereocenters. The presence in the furan diene of a susbtituent at the 3-position bearing an atom with lone-pair electrons propitiates the coordination of a metallic atom by the sulfoxide and the R3 “ligand” group. This chelation effect, together with the stereoelectronic demand of the R3 and sulfoxide groups, considerably decreases the degree of conformational freedom of the diene moiety in the cyclic transition state leading to the observed stereoselectivity. By choosing appropriate substituents in the furan ring, it is possible to obtain 100:0 cis-trans and 100:0 endo-exo diastereoselectivities. Up to 100 % π-facial diastereoselectivity (enantioselectivity after removal of the sulfoxide group) could be reached. Yields lie within the range of 50–80 %, depending on the furan substrate. However, if the furan diene is fitted with deactivating electron-withdrawing substituents, low conversions were observed under certain reaction conditions, but always with excellent-to-complete chemo- and stereoselectivities. The conversion and yield increase on introduction of an electron-donating substituent at the C-3 of the furan ring.

Several C-3 substituted furans with chelating groups have been reacted with 2,3-dibromo-3-pentanone in the presence of a reducing metal, resulting in the formation of [4+3]-cycloadducts with complete cis–trans and endo–exo diastereoselectivity and in excellent yield. A certain variability of the conversion and reaction yield could be observed, when changing the reaction conditions, but in all cases the stereoselectivity was complete, compared to that of C-3 substituted furans with non-chelating groups. Also, a general method of assignment of stereochemistry of cycloadducts has been established by NMR, considering diagnostic patterns of signals with different multiplicity and chemical shifts depending on the stereochemistry of diastereomeric cycloadducts.

A variety of C-3 functionalized chiral sulfoxide-containing furan derivatives is prepared, mainly based on manipulation of the carboxyl-moiety in (III).