Adamantanethione

Kaiser and Wulfers reported the first example of a thietane formation reaction involving photolysis of thiobenzophenone with olefins [27]. Since then a large number of systems have been reported. Thiobenzophenone and related compounds, xanthione and related compounds, the a,p-unsaturated thiones such as thiocoumarin, and adamantanethione have been most thoroughly examined. The wavelength dependence of these reactions has been systematically investigated in order to ascertain differences, if any, in the photochemistry of the thione S2 and T states. Scheme 1 shows one example of photocycloaddition of... 

Acidic compounds of type R—XH, which are able to protonate thiocarbonyl ylides, also undergo 1,3-addition leading to products of S,S-, S,0-, or 5,A-acetal type (Scheme 5.20). Thiophenols and thiols add smoothly to thiocarbonyl ylides generated from 2,5-dihydro-l,3,4-thiadiazoles (36,38,86,98,99). Thiocamphor, which exists in solution in equilibrium with its enethiol form, undergoes a similar reaction with adamantanethione (5)-methylide (52) to give dithioacetal 53 (40) (Scheme 5.21). Formation of analogous products was observed with some thiocarbonyl functionalized NH-heterocycles (100). 

Catalyst-mediated decomposition of diazo compounds in the presence of C=S compounds has found application for the preparation of thiiranes in homogeneous systems (68,110,111). Recently, a convenient procedure for the preparation of geminal dichlorothiiranes from nonenolizable thioketones and chloroform under Makosza conditions was reported (112). Another approach to 2,2-dihalogenated thiiranes (e.g., 2,2-difluoro derivatives) involves the thermolysis of Seyferth reagents in the presence of thioketones (113,114a). Nucleophilic dimethoxycarbene was shown to add smoothly to adamantanethione to provide a unique approach to a thiiranone (5, 5 )-dimethylacetal (114b). 

Numerous examples involving the preparation of tetrahydrothiophenes via [3 + 2] cycloaddition of thiocarbonyl ylides with electron-poor alkenes have been reported. Thiobenzophenone (5)-methylide (16), generated from 2,5-dihydro-1,3,4-thiadiazole (15) and analogous compounds, react with maleic anhydride, N-substituted maleic imide, maleates, fumarates, and fumaronitrile at —45°C (28,91,93,98,128,129). Similar reactions with adamantanethione (5)-methylide (52) and 2,2,4,4-tetramethyl-3-thioxocyclobutanone (5)-methylide (69) occur at ca. +45°C and, generally, the products of type 70 were obtained in high yield (36,94,97,130) (Scheme 5.25). Reaction with ( )- and (Z)-configured dipolaro-philes stereospecifically afford trans and cis configured adducts. 

The reaction of thiocarbonyl ylides with propiolates affords a mixture of regioisomeric cycloadducts. Thus, 2,5-dihydrothiophenes obtained from the reaction of adamantanethione (5)-methylide (52) and methyl propiolate were produced in a 1 1 ratio (95). In the case of ylide 69, the ratio was 1 2 in favor of the sterically less hindered isomer (160). 

The only reported reaction using phenylisocyanate as a trapping agent is one that involves adamantanethione (5)-methylide (52) as the dipole (163). Although a 1 1 adduct was isolated, its spectral data did not fully establish the structure of the... 

Related investigations of the reaction of diazo compounds with alkyl-substituted thioketones [R2C=S, R = Et, Pr, i-Pi, f-Bu (203) 2,2,4,4-tetramethylcyclobutan-l-one-3-thione (204), and adamantanethione (205,206)] showed that the 3,3-dialkyl-... 

The isomeric adamantane-spirothiadiazolines (145 and 146) (Scheme 8.34) exhibit different thermal stability [145 Xi/2 = 33 min at 45 °C 146 Xi/2 = 25.6 min at 110 °C (206a)]. Elimination of N2 from 145 generates thiocarbonyl ylide 147 that was trapped not only with the dipolarophiles mentioned above for 140, but also with aldehydes and imines (206a) (147 —> 149). Without a trapping reagent, thiirane 151 was formed from both 145 (at 80 °C) and 146. In the latter case, the extrusion probably proceeds via intermediate 148 and is accompanied by homo-adamantanethione 152 and a trace of methyleneadamantane. When 145 was decomposed at 45°C rather than at 80 °C, dimer 150 was also obtained. The isolation of 150 suggests that ylide 147 is also able to act as a base toward its precursor 145 (213). In fact, 147 can also be trapped with other protic nucleophiles. 

Thiagermirane (120) and alkylidenethiagermirane (121) are isolated in the reactions of dimesitylgermylene, generated from hexamesitylcyclotrigermane, with adamantanethione and di-tert-butylthioketene, respectively (Scheme 14.54). ... 

Thiocarbonyl ylides are both nucleophilic and basic compounds (40,41,86). For example, adamantanethione (5)-methylide (52) is able to deprotonate its precursor, the corresponding 2,5-dihydro-1,3,4-thiadiazole, and a 1 1 adduct is formed in a multistep reaction (40,86). Thioxonium ion (56) (Scheme 5.22) was proposed as a reactive intermediate. On the other hand, thiofenchone (S)-methylide (48) is not able to deprotonate its precursor but instead undergoes electrocyclization to give a mixture of diastereoisomeric thiiranes (41,87,88). The addition of a trace of acetic acid changes the reaction course remarkably, and instead of an electrocyclization product, the new isomer 51 was isolated (41,87) (Scheme 5.18). The formation of 51 is the result of a Wagner-Meerwein rearrangement of thioxonium ion 49. 

Thus, pentacarbonyl(thioketone) complexes [M(CO)5L] were prepared by irradiation of solutions of [M(CO)6] (M = Cr, Mo, W) in the presence of thioketones L (L = thiobenzophenone, adamantanethione)119 [Eq. (4)] and by refluxing solutions of [Mo(CO)6] in tetrahydrofuran (THF) in the presence of L = p,p -disubstituted thiobenzophenones, thiofenchnone, and thiocamphor, respectively.120 The formation of two diastereomers of the thiocamphor complex was observed, probably due to a high inversion barrier at sulfur. Only one isomer of the thiofenchnone complex could be detected. However, fluxional behavior could not be ruled out.120... 

Modifications of the route described earlier are (a) the conversion of [M(CO)6] (M = Mo, W) into the chloro-bridged binuclear trianions 10, which subsequently react with S = C(C6H4OMe-p)2 to give the thioketone complexes, and (b) reduction of [W(CO)6] by sodium amalgam to give the dianion [W2(CO)i0]2 and treatment of the latter with thiobenzophenones, adamantanethione, or thiocamphor (Scheme 3).128... 

Aliphatic and alicyclic thiones are less well investigated, principally because of their inherent instability. Adamantanethione, however, has been studied in detail and undergoes [ 2 + 2] cycloaddition to electron-deficient and electron-rich alkenes from both T, and S2 excited states. Addition from the latter is more efficient than that from the triplet and is again stereospecific but not regiospecific. Addition of adamantanethione (412) to ethyl vinyl... 

The 8 + 2-cycloaddition of 2//-cy c I o h cpta[h ] furan -2 - one (155) with acyclic 1,3-dienes provides a facile route to bicyclo[5.3.0] ring systems (156) (Scheme 61).291 2H-Benzo[Z>]thiete in the o-quinoid form undergoes 8 + 2-cycloaddition with 1,3-dithiolane-2-thione, l,3-dithiole-2-thiones, and adamantanethione to produce 4//-1,3-benzoditliianes.292... 

In recent years, P4S10 has been successfully applied to the synthesis of bridged thioketones (adamantanethione, thiofenchone and thiocamphor)253 and other bicyclic thiones254 (equation 25). 

Thiobenzophenone and adamantanethione react with sulfur (1 1) under catalysis by sodium thiophenoxide in acetone at room temperature furnishing 1,2,4,5-tetrathianes in high yields. With more sulfur, adamantanethione produces l,2,3,5,6-pentathiepanebis(spiroadamantane), which interconverted with the tetrathiane, but not with the 1,2,4-trithiolane < 1997H(45)507>. 

Semi-empirical calculations for the geometry and dipole moment of tetrasubstituted bis-spiro-l,2,4-trithiolanes derived from adamantanethione were reported <2004JMT(668)179>. Satisfactory agreement with X-ray data was obtained with the PM3 method. 

The metathesis equilibration between adamantanethione 216 and trithiolanes 215 is driven to the right (82% yield) via the intermediate thiosulfine 218 on refluxing in CHC13 probably by the conjugation energy of the thiobenzophenone. With an excess of adamantanethione the monospiro-trithiolane affords at 130 °C a dispiro-trithiolane 219 (Scheme 72) <1997T939>. 

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