Thietes, photolysis

The photolysis of various substituted thiete dioxides under similar conditions resulted in the formation of the unsaturated ketones (255)264, most probably via a vinyl sulfene intermediate followed by a loss of sulfur monoxide as shown in equation 96. The same results were obtained in the thermolysis of 6e (R1 = R3 = Ph R2 = R4 = H)231, which further demonstrates that similar mechanisms are operative in thermolyses and pho-tolyses of thietane dioxides and thiete dioxides. 

Naphtho[ >, c]thiete (75) was obtained with high yield as a stable compound on photolysis of (74) or (76). Nitrogen and oxygen analogues of (75) are unstable, but can in some instances be trapped. 

Unlike naphtho[6c]oxete, described previously, its thio analog 20 is a stable compound which can be obtained in high yield (97-100%) on photolysis of naphtho[c[Pg.8]

IJOC4570). Photolysis or thermolysis of naphtho[ c]thiete 20 and naph-tho[carbon disulphide, also occurs by a free-radical mechanism which leads to naphtho[other products of these conversions [79JA7684 81JCS(P1)413]. 

The mass spectral fragmentation patterns of a variety of fused and spiro thietanes and thietes were presented in CHEC(1984) and CHEC-II(1996). Only more recent data are included here. The mass spectrometry (MS) spectra of thietanes 10 and 11 show molecular ion peaks at m/z 330 and 270, respectively, corresponding to the molecular weights of thiobarbiturates used for their preparation by photolysis in acetonitrile <2003H(59)303>. The structures of different derivatives (substituted in the thietane ring by CH3, Ph, or OC2H5 groups) of 5,7,7,9-tetramethyl-l-thia-... 

An attempted synthesis of thiete by thermolysis (300°) of a Diels-Alder adduct with anthracene was unsuccessful, no doubt because of the thermal instability of thiete.Thiete derivative 215 was obtained by other methods, and structure 217 was suggested as an intermediate in the desulfurization of 216. The unusual dithiolactone 218b is formally derived from a cycloaddition of carbon disulfide with acetylene 218a. " A 2-substituted-3,4-diphenyl-2H-thiete is obtained by treatment of the ylide, 8-methyl-1,3-diphenyldibenzo [e, h]-8-thiazulene, with diphenylcyclo-propenethione. 2-Methoxy-3,4-diphenyl-2H-thiete is one of several products obtained on photolysis of diphenylcyclopropenethione in methanol. ... 

The first thiete fused to an aromatic system 219 (and an anthracene derivative) was reported in 1965 and was prepared by reduction of a naphthothiete sulfone. An attempt to prepare benzothiete by desulfurization of benzo-l,2-dithiolane was unsuccessful. Photolysis of benzo-l,2-dithiolane 1,1-dioxide in an attempt to extrude sulfur dioxide to give benzothiete also was unsuccessful. The naphthothiete 205, however, was prepared by extrusion of sulfur dioxide from 220 and nitrogen from 221. Thiete 205 also is obtained in 6-8% yield by treatment of 1,8-dehydronaphthalene with carbon disulfide. The unstable thiolactone 211 was formed by a photochemical extrusion of benzaldehyde from 222 and from 222a at 350°C. The benzothietes 209, 223, " and 224 have been... 

A different approach was used for the synthesis of the naphtho[ 1,2]thiete 1,1-dioxide 272. The peri-naphthothiete sulfone 20Sb is prepared by photolysis Qf 271612.613 oxidation of the sulfide 205. = ... 

Electrolysis of benzothiete sulfone 269 yields the phenylmethanesulfinate anion (major) and the o-toluenesulfinate anion (minor).Thermolysis 618,619 gj. photolysis of thiete 1,1-dioxides proceeds via ring-opening to vinyl sulfines, for example. 288, which have been trapped by reaction with water, phenol,methanol, or norbornenes. These intermediates may recyclize to unsaturated sultines (cyclic sulfinate esters) (e.g., 289) or lose sulfur monoxide to give mainly the trans isomers of a,j3-unsaturated carbonyl compounds (e.g., 290). Mass spectra also indicate the formation of unsaturated sultines. ... 

The sulfur-sulfur interatomic distance in 9-phenyl-4,8,10-trithiadibenzo[cd,ij]a-zulene-8-oxide (417) is significantly shorter than the sum of their van der Waals radii and photolysis of (417) and (418) yields (420) and aldehydes or ketones (421) quantitatively. The unstable primary photoproduct (419) may be isolated and photolyses to (420) and (421). A similarly short sulfur-sulfur interatomic distance is found in a series of naphtho[l,8-ef][l,4]dithiepins and direct irradiation yields naphtho[l,8-cd][l,2]dithioles quantitatively with analogous S-S bond formation and alkene elimination. Photolysis of compounds (422), (424) and (426) gives the dimerised disulfides (423), (425) and (427) in 45%, 17% and 1% yields respectively. Irradiation of the tetraalkyl-2H-thietes (428) at 254 nm leads to a photostationary mixture containing the purple enethiones (429) (25%). Exposure of the mixture to 300 nm radiation induces almost complete reversion to (428). ... 

Thus, the best laboratory procedure for preparation of naphtho[l,8-Z c]thiete (34) is the photolysis of naphthothiadiazine (42). 

Inasmuch as naphtho[l,8-Z c]thiete (34) was successively prepared by photolysis and thermolysis of naphthothiadiazine (42), Nakayama et al. (79JA7684) hoped to obtain in the same fashion naphtho[l,8-Z)c]thiete S-oxide (35) from naphtho[l,8-t/c]-1,2,3-thiadiazine S-oxide (50, Scheme 8). They attempted to synthesize sulfoxide 50 by oxidation of thiadiazine (42) with m-chloroperbenzoic acid (m-CPBA). However, this reaction carried out at room temperature with an equivalent amount of m-CPBA occurred with nitrogen liberation and with the formation of naphtho[l, 8-Z)c]thiete S-oxide (35) in 71% yield instead of the expected sulfoxide (50). 

Other work on four-membered heterocycles containing one sulphur atom includes a study of the vacuum-u.v. photodecomposition of thietan 1,1-dioxide and the formation of a thietanone from a xanthate and diphenylketen, and reports of several thiets. There is evidence that photolysis of (107) in a matrix at 77 K leads to the o-thiobenzoquinone (108), which is interconvertible with the... 

Further reactions of tetrakis(trifluoromethyl)- Dewar thiophen have been reported. The half-life for reversion to the normal thiophen is 5.1 h at 160 °C, in benzene. The isomerization occurs at room temperature in triphenylphosphine in DMSO, a dimer (46) precipitates immediately. Diels-Alder reactions with butadienes, furan, pyrrole, and cyclopentadiene give the expected products. The furan adduct is converted into an oxahomocubane by photolysis, after desulphurization. Heating of the azide adduct (47) leads, after desulphurization, to pyrroles through a thiet intermediate. Under the same conditions, the hydrazoic... 

Thiets.—Thiete (111a) and its simple derivatives e.g. 111b) were prepared some years ago they are labile and tend to polymerize. The corresponding 1,1-dioxides 2ire considerably more stable. Stabilization of thiete by annelation with a benzene ring has now been achieved with the synthesis of (114), prepared by the photolysis of (112) the isomer (113) was obtained by acid hydrolysis of (112). ... 

Photolysis of thiet 1,1-dioxides (179), either at 235 nm or at 350 nm with a sensitizer, yields unsaturated ketones (181) by loss of sulphur monoxide from a vinyl sulphine intermediate (180). A small amount of cyclohexadiene... 

---