Dibenzo oxathiins

The aminolysis of dibenzo[l,2]oxathiin 6-oxide 10 with primary and secondary amines in water was quantitively followed by the absorption at 270 nm in UV spectroscopy, from which the reaction was found to obey pseudo-first-order kinetics < 1999TL8901 >. Because of the lack of a distinct difference in the magnitude of y obs between primary and secondary amines, and between acyclic and cyclic amines, the aminolysis reaction must proceed in two steps the first is a fast formation of intermediate 102 followed by a second slow decomposition step to the reaction product 103 (Scheme 24). 

The UV photoelectron spectra of 1,4-dioxin, 1,4-dithiin, 1,4-oxathiin, and their dibenzo derivatives as well as the saturated compounds were detailed in CHEC(1984) <1984CHEC(3)958>. 

Desulfurization reactions in the 1,2-series are encountered among derivatives of both oxathiins and dithiins. 1,2-Oxathiin 2,2-dioxides extrude sulfur dioxide at elevated temperature over zinc oxide, iron or copper oxide to give the corresponding furan (66HC(21 -2)789) [cf. Section 2.26.3.1.2). Copper is a good catalyst for the extrusion of sulfur and sulfur dioxide from dibenzo[c,e3[l,2]dithiin (40) and its dioxide respectively to give dibenzothiophene (66HC(21-2)968). 

Dibenzo[c,e][ 1,2]oxathiin 6-oxide MS, 3, 957 (81JOC2373) Dibenzo[i/]phosphonin, 7-phenyl- H NMR, 7, 713 (80JA4838) Dibenzo[d/]phosphonin 7-oxide, 7-phenyl- H NMR, 7, 713 (80JA4838) Dibenzo[d/]phosphoninium, 7-methyl-7-phenyl- H NMR, 7, 713 (80JA4838)... 

The central ring of both dibenzo[l,4]- dithiins and -oxathiins is cleaved on treatment with Li and a catalytic amount of 4,4"-di-rert-butylbiphenyl (DTBB) to afford thiols after reaction of the dilithio intermediate with electrophiles. In certain instances, the initial product can be cyclised to the dibenzo- dithiepine and -oxathiepine <02CL726>. The dilithio salt from thianthrene reacts sequentially with two different carbonyl compounds to give a l,2-di(hydroxyalkyl)benzene. When C02 is used as the second electrophile, a phthalan results <02TL7205>. 

Dibenzo-l,4-oxathiine 2,8-Dinitro-E9a, 58f. [2-(4-ND2-phcnoxy) 5-N02 -1 -S02H - benzene/H +]... 

Dibenzo-l,4-oxathiine 8-Methyl-2-nitro- E9a, 58 [2-(4-CH3-phenoxy) — 5-N02 — 1 -S02H -benzene/11+]... 

Annulation with oxathiin (synthesis of dibenzo-l,4-oxathiin)... 

Pyridine, the diazines, 1,3,5-triazine, 1,2,4,5-tetrazine, quinoline, isoquinoline, quinolizinium ion and the benzodiazines are HtiCKEL-aromatic systems (heteroarenes). 2//-Pyrane, 4//-pyrane and the corresponding benzo compounds, 1,4-dioxin, 1,4-dithiin and 1,4-oxathiin are not aromatic. However, the cations derived therefrom, like pyrylium and thiinium cations or dioxinium and dithiinium dications are aromatic the same is true for the corresponding benzo or dibenzo systems (e.g., benzopyrylium). Phosphinin is characterized by a specific heteroaromatic situation. 

Pseudo-first-order rate constants (kou) have been measured for aminolysis of dibenzo-[l,2]oxathiin-6-oxide (166) (Scheme 29). The plot of fcobs vs amine concentration exhibits a downward curvature which levels off as the amine concentration increases. Such a downward curvature is proposed as definitive evidence for a stepwise mechanism, which is supported by the microscopic rate constants determined. ... 

Benzo- and Dibenzo-1,4-dithiins.—An improved synthesis of benzo-l,4-dithiin and -oxathiin is based on a novel intramolecular sulphenylation of the thiol-sulphonates PhY(CHa)2SSOaMe (Y = S or O) in the presence of aluminium chloride. Phenyl-lithium reacts with bromobenzene and carbon disulphide to give 2,3-diphenyl-l,4-benzodithiin via a benzyne intermediate. ... 

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