Cycloaddition reactions of sulphines and thiones with azoalkenes

Abstract

Fluorenethione S-oxide undergoes (2 + 4) cycloadditions with azoalkenes to yield 2H-1,2,3-thiadiazine 1 -oxides together with a small amount of the regioisomeric 6H-1,3,4-thiadiazine 1 -oxides. Fluorenethione, with azoalkenes, undergoes (2 + 4) regiospecific cycloaddition reactions leading to the formation of 6H-1,3,4-thiadiazine derivatives. Diarylsulphines and diarylthiones fail to react with azoalkenes.AZOALKENES are well known to undergo (4 + 2)-type cycloaddition reactions with a variety of carbon-carbon dienophiles and heterodienophiles 5 9 6 leading to the formation of six-membered heterocyclic compounds. C,,H2,N,0S and mass spectra showed their molecular ions at nzle 496.Mass spectra of both ( 6a) and (6b) showed the same fragmentation pattern with prominent peaks at mle 357 ( M + -PhNSO) and 139 (PhNSO), in agreement with R' * One of the referees pointed out that the sulphinyl oxygen in ( 7) is almost certainly tvans-oriented with respect to the adjacent phenyl group, owing to steric requirements for peroxyacid oxidation of sulphides to sulphoxides.

Thionations Using a P4S10−Pyridine Complex in Solvents Such as Acetonitrile and Dimethyl Sulfone

“…Benzaldehyde has been thionated many times in the past, − and the product has invariably been isolated as the trimer ( 30 ) of the unstable primary product 29 (Figure ), and the trimer 30 , was indeed the product when benzaldehyde was reacted with the reagent 3 in dimethyl sulfone.…”

Cyclohexenylphenyldiazene: A Simple Surrogate of the Azobenzene Photochromic Unit

“…The addition of arylhydrazine gives the corresponding arylhydrazone, a labile intermediate, that affords arylazoalkene by treatment with a mild base that promotes a clean 1,4-elimination of HX . Typical reactions of arylazoalkenes are: (i) the conjugate addition of nucleophiles 19a, to the azo−ene moiety and (ii) the 4 + 2 cycloaddition reactions with a variety of carbon−carbon dienophiles and heterodienofiles, leading to the formation of six-membered heterocyclic compounds …”

Hetero-Diels-Alder Reactions of In Situ-Generated Azoalkenes with Thioketones; Experimental and Theoretical Studies

“… Comparison of the course of hetero -Diels-Alder reactions of thiofluorenone ( 1b ) and the corresponding S -oxide (sulfine) with stable, isolable azoalkenes ( 4a , b ) [ 32 ]. …”

“…However, a single, brief report by B. Bonini et al on the hetero -Diels-Alder reaction of thiofluorenone ( Scheme 2 ( 1b )) with some stable, isolable azoalkenes ( Scheme 2 ( 4a , b )) appeared in 1981. These reactions were performed at room temperature in benzene solution and regioselectively led to 3,6-dihydro-2 H -1,3,4-thiadiazines ( Scheme 2 ( 5a , b )) in high to fair yields ( Scheme 2 ) [ 32 ]. Notably, thiofluorenone S -oxide (sulfine), derived from the studied aromatic thioketone, reacted with Scheme 2 ( 4a ) and Scheme 2 ( 4b ) to give the corresponding S -oxides Scheme 2 ( 6c ) and Scheme 2 ( 6d ), respectively, derived from isomeric 1,2,3-thiadiazines as major products, however ( Scheme 2 , below).…”