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Uncatalyzed cycloadditions of (RS,E)-1 and (RS,Z)-3-[(1S)-isoborneol-10-sulfinyl]-1-methoxybuta-1,3-diene 2 with maleimide and N-phenylmaleimide occurred with complete endo and very high facial diastereoselectivities. The effects of Lewis acid catalysis on these Diels–Alder reactions have been evaluated. LiClO4 catalyzed cycloaddition of 1 with dimethyl maleate gave cyclohexene 13 as the unique product with complete control of endo and π-facial diastereoselectivities exerted by the sulfinyl group. A significant improvement in diastereoselectivity was also observed in the LiClO4 catalyzed cycloaddition of 1 with dimethyl fumarate.

Uncatalyzed cycloadditions of enantiopure [(1 S )-isoborneol-10-sulfinyl]- and [(1 S - exo )-2-bornylsulfinyl]vinylcyclohexenes with N -phenylmaleimide occur with good facial diastereoselectivity, controlled by the sulfur configuration, even if the extent of this stereoselection appears influenced by the structural features of the terpene residue directly linked to the sulfoxide moiety. Complete endo diastereoselectivity is observed in LiClO 4 catalyzed cycloadditions of ( R S )-1-{1-[(1 S )-isoborneol-10-sulfinyl]- and ( S S )-1-{1-[(1 S-exo )-2-bornylsulfinyl]vinyl}cyclohexenes 4 and 5 , respectively. The Diels–Alder reactivity of 5 and ( S S , E )-1-{2-[(1 S-exo )-2-bornylsulfinyl]vinyl}cyclohexene 7 , with the chiral auxiliary being in a different position with respect to the diene moiety, is also compared, and the results obtained comfirm that 1-sulfinyldienes are less reactive than 2-sulfinyldienes. SnCl 4 catalyzed cycloaddition of 7 with N -methylmaleimide is also performed.

Uncatalyzed and LiClO4 catalyzed cycloadditions of (RS)-1-{1-[(1S)-isoborneol-10-sulfinyl]vinyl}cyclohexene 1 and (RS,E)-3-[(1S)-isoborneol-10-sulfinyl]-1-methoxybuta-1,3-diene 2 with di(p-tolyl)- and di(p-anisyl)thioketones 3 and 4 occur with complete regioselectivity. The lack of facial diastereoselectivity, observed in the cycloadditions of 1 with 3 or 4, appears to be a consequence of the sterical features of both diene and dienophile which, in the transition states, make the topological differentiation induced by the presence of the alkylsulfinyl group as chiral auxiliary uninfluential. No significant improvement in diastereoselectivity is observed in the LiClO4 catalyzed reactions, but the obtained enantiopure cycloadducts are easily separated by column chromatography and isolated in high yields. © 1999 Elsevier Science Ltd. All rights reserved.

The unexpected and previously unknown TMSI-promoted conversion of a,b-unsaturated sulfoxides into carbonyl compounds and disulfides is described. It occurs in good yields under mild conditions. The examples provided support the generality and eAciency of this procedure which acts as a good method for removing the sulfinyl group with the advantage of transforming the vinyl sulfoxides into carbonyl compounds. # 2000 Elsevier Science Ltd. All rights reserved.

This review (56 references) provides a comprehensive survey of the literature on sulfenic acid chemistry from 1990 through June 2006, focusing the attention on salient aspects of their structures and involvement in organic processes. Even if the majority of known sulfenic acids cannot be isolated, some stable ones have been obtained, and their study helped dramatically the comprehension of chemical and physical properties of all sulfenic acids and indirectly of the role that Cys-SOHs play in protein biochemistry. Many papers have been published in the last fifteen years about the sulfenic acid intermediacy in organic chemistry. Once generated, they can be involved in intraand intermolecular additions to unsaturated molecules. Few examples of sulfenic acid addition to double bonds have been recently described and most of them are intramolecular processes, whereas the addition of enantiopure sulfenic acids onto carbon-carbon triple bonds has been widely exploited in the synthesis of vinyl sulfoxides to be used in many stereoselective transformations. The thermic -elimination from sulfinyl precursors is a way to generate sulfenic acids but it has been also used for removing the sulfinyl moiety from organic molecules and forming double bonds with controlled stereochemistry. Some significant applications of extrusion processes are also described in the present review.

New heterotricyclic systems, 6,10a,11,11a-tetrahydro-5H-bis[1,2,4]oxadiazolo[4,5-d:5′,4′-g][1,4]diazepines 6,7,9-11 and 5,6,10,10a,11,11a-hexahydro-1H-bis[1,2,4]triazolo[4,3-d:3′,4′-g][1,4]diazepines 8,12 have been obtained by double site- and regie-specific 1,3-dipolar cycloaddition of mesitylnitrile oxide (1) or diphenylnitrile imine (2) to 5,7-disubstituted 2,3-dihydro-1H-1,4-diazepines 3-5. The structure of the synthesized bis-adducts 6-12 shows that the hetero double bonds are much more reactive than the olefinic ones in the dipolarophiles under study. No evidence for the formation of mono-adducts was obtained.

The absorption and emission properties of $[Pd(terpy)X]^+ \ (terpy=2,2^': 6,2^"-terpyridine,X=I,Cl,NO_2N_3)$ have been investigated. For comparison purposes, the same properties of the free terpy ligand have also been studied. The absorption spectra are almost solvent independent and quite similar for all the complexes studied, thus indicating that the most prominent bands are due to ligand-centred (LC) tansitions. The lowest energy band, however, is red-shifted with respect to that of the free terpy ligand by about 8100 $cm^-^1$, suggesting a strong distortion of the ligand structure on coordination to the metal atom. All the complexes exhibit a structured, long-lived $(10^-^4-10^-^3_s)$ emission in butyronitrile at 77 K, with energy and bandshape quite similar to the long-lived (13ms) phosphorescence of the free terpy. The dependence of the emission lifetime on the nature of the X ligand is briefly discussed.

Four representatives of the new ring system [3,1]benzoxazino[2,1-b][1,3]benzoxazine, as determined by X-ray crystallography, were prepared by reaction of N-(2-hydroxybenzyl)anthranilic acids with trifluoroacetic anhydride.

The double ring closure of N-(2-hydroxybenzyl)anthranilic acids 1 with acetic anhydride or its acyclic analogous (RCH2CO)2O 2b and 2e lead to the formation of novel 12H-quino[2,1-b][1,3]benzoxazin-5-ones. The structure of the obtained compounds was proved with the use of their ir, mass, 1H and 13C nmr spectra. Homo- and heteronuclear two-dimensional nmr experiments were performed to unambiguously assign all proton and carbon chemical shifts.