1.2- Dithiole-3-thiones reactions

Thio and thiol substituents Reactions with dipolarophiles Atropisomeric 1,2-dithiole-3-thiones Reactions involving organometallic compounds... 

Recently, it has been reported that l,3-dithiole-2-thione (12) reacts with primary amine to give the corresponding thiourea and A-4-thia2oline-2-thione (Scheme 5) (14). 5-Methylenethiazolidine-2-thione (13) obtained from the reaction of propargyl amine and carbon disulfide... 

Few isothiazoles undergo simple cycloaddition reactions. 4-Nitroisothiazoles add to alkynes (see Section 4.17.7.4). With 5-thiones (84) and dimethyl acetylenedicarboxylate, addition to both sulfur atoms leads to 1,3-dithioles (85) (77SST(4)339, 80H(14)785, 81H(16)156, 81H(16)595). Isothiazol-3-one 1-oxide and the corresponding 1,1-dioxide give normal adducts with cyclopentadiene and anthracene (80MI41700), and saccharin forms simple 1 1 or 1 2 adducts with dimethyl acetylenedicarboxylate (72IJC(B)881). 

From the reactions of sulfur and carbon disulfide with cyclic ketone-derived enamines (570-573) 3H-l,2-dithiole-3-thiones were obtained, whereas the addition of carbon disulfide to other enamines gave a-dithio-pyrones (574), through initial dimerization of the enamine. 

Of greater importance is the reaction of unsaturated compounds with sulfur at 200-250°C, which normally leads to l,2-dithiole-3-thiones (trithiones) but especially with 2-aryIsubstituted 2-butenes and 1- aryl- or 2-aryl-1-butenes, thiophenes are obtained in 15-60% Thus p-methoxy-a-ethylstilbene (50) gives 2-phenyl-3-... 

A range of 4-substituted l,3-dithiole-2-thiones (71) and 2,6-substituted 1,4-dithiafulvalenes (73) were synthesised from 4-substimted 1,2,3-thiadiazoles (72). Reaction of (72) with NaH in a mixture of CS2 and acetonitrile led to the formation of (71), whereas absence of CS2 gave fulvalenes (73). This route was found to be very efficient for the preparation of 4-formyl-1,3-dithiole-2-thione (71 R = CHO), which was previously difficult to prepare, and thus allowed the synthesis of the novel 2,6(7)-bisformyltetraAiafulvalene (74) <96T3171>. 

Examples of reactions involving replacement and cyclization are the long-known preparation of thiophenes (89) from 1,4-diketones, and the formation of l,2-dithiole-3-thione (90) from the salicylate ester analog (91).120 In the latter instance, oxidative cyclization with formation of an S—S bond has occurred this is a common feature of these reactions, particularly if such a link is needed to complete a five-membered ring. Another example of this aspect is afforded by the reaction of the propane-1,3-dione derivatives (92) which yield 3,5-diaryl-1,2-dithiolylium salts (93) when heated with phosphorus pentasulfide in carbon disulfide, followed by perchloric acid.121... 

Interestingly, the introduction of two bromomethyl functions in 4- and 5-positions of ethylen-l,3-dithiole-2-thione leads to a packing determined by weak interactions involving also the bromine atoms. One I2 molecule behaves as an acceptor towards S and as donor towards the second I2 molecule, which in turn behaves as donor towards the a c Br orbital (Figure 13). Intermolecu-lar S- -Br, CFF Br and L -I contacts make up a three-dimensional network.480 Reaction of 5,5-dimethyl-2-selenoxoimidazoline-4-one with iodine provided the first structurally characterised compound of the type [RR C Se — I-I].32 The Se-I bond is shorter (269.9 pm) and the I-I contacts are longer (296.2 pm) than in 1 1 adducts of dialkylselenides with iodine (see Chapter 8.2). 

In all the reactions discussed in this section, both isopropyl groups were transformed into a 1,2-dithiole ring. When N-alkyldiisopropylamines and sulfur monochloride were mixed in chloroform in the absence of another base, that is, DABCO, two monocyclic dithiole-3-thiones 93 and 94 were isolated. 5-Mercapto derivative 93 was the main product in all the cases examined (2001MC165, 2006RCB143 Scheme 45). 

Two other N-substituted diisopropylamines (R = CH2CH2C1 and CH2CH2Phth) in the same reaction gave dithiolothiazine 95 which had apparently resulted from the HCl or phthalimide extrusion from 5-mercapto-l,2-dithiole-3-thiones 94 (Scheme 46). 

Structurally similar 5-chloro-l,2-dithiole-3-thiones 97 were obtained upon treatment of N-(2-phthalimidoethyl)-N-alkylisopropylamines with sulfur monochloride and DABCO and a final reaction with tiiethylamine (20030L929). The stability of thiones 97 is explained by the dipole-dipole interaction between the electron-rich l,2-dithiole-3-thione ring and electron-poor phthalimido groups (Scheme 48). 

The reaction of diisopropyl sulfide with sulfur monochloride and DABCO afforded l,2-dithiolo-3-thiones 98 and 99 (1999JOC4376). Dithiole ring formation had been assumed to be similar to that produced from tertiary diisopropyl-amines. However, in the case of diisopropyl sulfide only one isopropyl group was... 

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... 

Ethylenediaminetetraacetic acid, analogs, complexes of, 3 277 chelation by, 3 276-277 cobalt complex of, 3 281 complexes, 3 277-278 formation constant of, 3 273-274 -nickel, 3 17-18 stability of, 3 266-267 reaction with metal ions, 3 62 Ethylene dibromide, irradiation of, 5 196 4,5-Ethylenedithio-1,3-dithiole-2-thione based supramolecular complexes, 46 200-204 Ethylene glycol, 32 4... 

Some years later, the first stable thiocarbonyl ylides 9 and 10 were prepared by the reaction of thiourea with cyano-substituted oxiranes (19,20) or by addition of Rh-di(tosyl)carbenoid to benzo-l,2-dithiole-3-thione (21), respectively. Enhanced stability and the low reactivity of 9 and 10, which enables their isolation in crystalline form, results from the push-pull substitution at the two termini [cf. also (22)]. Another class of stable thiocarbonyl ylides that are also able to afford [3 + 2]-cycloaddition products are the mesoionic 1,3-dithiole-4-ones of type 11 (23,24). 

SM(68)1914>. Trimethyl phosphite 102 (lOequiv) mediated cross-coupling between the l,3-dithiole-2-thiones 103 and the ketone 40 yielded unsymmetrical TTF derivatives 45-48, in moderate yields (Scheme 7)<1997SM(86)1871>. Similar reaction between the 2-thione 104 and the TTF derivatives 105 yielded the pentacycles 88 (yields were not recorded) (Equation 2) <1997SM(86)1821>. 

---