1.2.4- Dithiazole-3-thiones, reaction with

Reaction of 5-phenyl-3//-l,2,4-dithiazole-3-thione (84) with 1,2-diphenylcyclopropenone leads to the SS bridged ring-opened cyclopropenone product (85) (70%) and the trithiaheterapentalene bicycle (25 R = Ph)(7%) which is believed to result from thermal decomposition of (84) (Equation... 

Some reactions concerning the thione group of dithiazole thiones (126) have been discussed (see Section 4.14.5.7). As expected, the thione group is methylated with Me2S04 affording, after treatment... 

Several workers have studied the reactions of l,2-dithiole-3-thiones and related systems with acetylenic esters. The thiones (395), for example, react with DMAD to give 2-thioacylmethylene-l,3-dithioles (396), which may arise through a concerted 1,3-dipolar addition to the S—C=S moiety. These adducts undergo further reaction with DMAD, yielding thiopyran-4-spiro-2 -(l,3-dithioles) (397) (Scheme 62). Similarly, the reaction of 5-phenyl-l,2,4-dithiazole-3-thione (398) with... 

DMAD gives the adduct (399) [Eq. (60)]. The reaction of 5-amino-l,2,4-dithiazole-3-thione (400) with DMAD, however, gives rise to the initial adduct (401), which further reacts with DMAD to give 402... 

Primary and secondary alkylamines have been used for the preparation of iV-alkyl- and V,lV-dialkylcyanothio-formamides, respectively, in the reaction with 4-chloro-l,2,3-dithiazole-5-thione 41 (Equation 20) <1996TL3709>. 4-Chloro-l,2,3-dithiazole-5-one 99 in the reaction with mono- and di-alkylamines afforded N,N -disubstituted ureas in moderate to good yields (Equation 21) <2001TL8197>. The reaction was proposed to be similar to the corresponding thione 41 but displacement of a cyano group by another molecule of alkylamine accompanies this conversion. 

Aryl-l,2,4-dithiazole-3-thiones react with phenylacetylene giving two compounds, namely, A-(4-aryl-l,3-dithiol-2-ylidene) thiobenz-amide (52) and 2,5-diaryl- 1,6,6a IV-trithia-3-azapentalene, which may also be considered as AT-(5-aryl-l -dithiohS-ylideneJthiobenz-amide (53). This compound is converted into the corresponding benzamide (54) by mercuric acetate oxidation, the opposite reaction being realized with phosphorus pentasulfide.79... 

For the l,2,4-dioxazol-3-one (65 R1 = Ar, X = Z = 0) (72JPR145), nucleophilic addition by secondary amines occurs at the ring C=N to give the adduct (90), and while I gives a high yield of benzamide, the site of attack in this case is less clear. In contrast, the l,2,4-dithiazole-3-thione (30) is attacked by arylamines at the thione carbon with extrusion of sulfur, in a reaction analogous to that in Scheme 15. A similar reaction occurs with the isomeric 1,2,4-dithiazolidine derivatives (41 X = 0, S) (72IJC1138). 

When 3-benzoylimino-5,6-dihydro-37f-imidazo[2,l-c][l,2,4]dithiazole (19) is treated with methanol or ethanol in the presence of sodium hydroxide 0-alkyl-A-[2-(2-alkyl-l-benzoyl-3-iso-ureido)ethyl]thiocarbamates (119) are formed as a result of the opening of both rings. Under analogous conditions the reaction with n-propanol affords imidazolidine-2-thione (120) and the sodium salt of Y-benzoyl-O-propylcarbamate (121) (Scheme 5) <868751 >. 

The reaction of benzoylthiourea with phosphorus pentasulfide was reported to yield 3-phenyl-l,2,4-dithiazole-5-thione (85).203 Derocque et al.20i observed that phosphorus pentasulfide converted 1,3-di benzoyl -2-methyl-2-thiopseudoureas into 86a. However, in view of the X-ray results on the analogous structure 84201 it may well be that structure 86b is a more important resonance contributor than 86a. 

When the reaction of 5-phenyl-l,2,4-dithiazole-3-one(thione) 65 (Ar = Ph, Y = 0, S) with trialkylphosphites is carried out under severe conditions (100 °C, 10 h), two different reaction centers in reactant 65 undergo an attack, namely the ring sulfur atom and the exocyclic sulfur or oxygen atom. In the first case, A-phosphorothioates 79 are formed. Bicyclic products 80 are the result of the second reaction pathway (Scheme 13) <1995JRM442, 1996PS557>. 

Scheme 21 Reactions of l,2,4-dithiazole-3-thiones with alkynes C02Me...

Cycloadditions with nitrile oxides occur across the C=S bond both with 1,3,5-oxathiazole-2-thiones (66JOC2417) and l,3,4-dithiazole-2-thiones (Scheme 28) (67BSF2239), the reaction proceeding via an interesting spiro compound which has been isolated in some cases. 

The formation of a number of oxathiazole and dithiazole derivatives by ring transformations of 1,2,4-dithiazolinimines (42) are illustrated in Schemes 22 and 25. Analogous reactions (Scheme 51) with thiadiazolimines (220) lead to the l,2,4-dithiazoline-5-thione... 

The starting material, which can also be considered as an a- (1,3 - dithiol-3 -ylidene) thioketone, is obtained by reacting alkynes with l,2-dithiole-3-thiones. These compounds when heated with elemental sulfur or sulfur-containing catalysts rearrange to l,6,6aA -trithiapentalenes as shown in equation (21). A mechanism has been suggested for this reaction (72CC540) but it should be noted that in the reaction of alkynes on l,2-dithiole-3-thiones or on 1,2,4-dithiazole-3 -thiones the final l,6,6aA 4- trithiapentalene is often obtained directly <7lAHC(l3)l6l,P. 191,199). 

Photoaddition of the dithiazole-3-thione (274 X = N) and of the dithiole-3-thiones (274 X = CH or CPh) to alkenes leading to formation of the 1,3-dithiolans (275) has been described.204 The reactions are non-stereospecific, the same mixture of isomers being obtained with cis- and trans-but-2-ene, and a radical pathway (Scheme 14) has therefore been proposed. Two separate reports... 

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