Dithiole-2-ones

Use of the /3-thiodithiocarbonates (25) and acid results in ring closure to the 1,3-dithiol-2-one (26). Methyl, ethyl and isopropyl groups have been utilized in (25) (76S489), and when R = f-butyl, ring closure occurred in the presence of perchloric acid with extreme ease (74JOC95). Other variations of this synthetic route to 1,3-dithiole derivatives are described in Chapter 4.32. 

Thieno[3,4-d][l,3]dithiol-2-one, 1-nitro-synthesis, 6, 1013 Thieno[3,4-c]furan, 4,6-dichloro-synthesis, 6, 1013 Thieno[3,4-c]furan, tetraphenyl-formation, 4, 1060 synthesis, 4, 1060 UV spectra, 4, 1044 Thieno[3,2-6]furans structure, 4, 1039 synthesis, 6, 1020 Thieno[3,4-c]furans... 

Iodoquinoxaline and 4-methyl-5-tributylstannyl-l,3-dithiol-2-one gave 2-(2-0X0-5 -methyl-1,3 -dithiol-4-yl)quinoxaline (63) (l-methyl-2-pyrrolidinone, 5°C, CuTC i, A, 40 min 44%). ... 

Alternatively, l,3-dithiol-2-ones have been obtained by reacting di-isopropylxanthogen disulfide with unsaturated substrates, such as disubstituted alkynes R2C2, in the presence of AIBN (azoisobutyrylnitrile), a radical initiator.78 Finally, vinylene dithiocarbonates can be obtained by reacting mer-cury(II) acetate with the corresponding trithiocarbonates, generated by reaction of electrophilic alkynes with ethylene trithiocarbonate.79 Analogously,... 

More recently, a new method was developed (05MI3) for photochromic 4,5-dithienyl(dibenzothienyl)-l,3-dithiol-2-ones 229 and dithiol-2-thiones 230 from acetylene derivative 228 (Scheme 66). Compounds 230 are good building blocks for the design of photochromic fluorophores. 

Synthesis of 2,3-dihydro-l,4-dithiin 11 was accomplished from l,3-dithiol-2-one 247 in the presence of dibro-moethane and potassium hydroxide <1998JOG3952>, while reaction of 2,3-dichloro-l,4-dioxane with powdered Zn in hexamethylphosphoramide (HMPA) was used for the synthesis of 1,4-dioxene 10 <1998JPP10067773>. To obtain substituted 1,4-oxathianes, the hydrogenation of the corresponding partially saturated compounds has been employed <2001J(P1)2604>. 

Thieno[3,4-3]thiophenes 500 were prepared from thiophen-3-yl-substituted [l,3]dithiol-2-ones 496 in good yields <2003JOG7115>. The photochemical irradiation of 496 leads to thieno[3,4-f]dithiines 497 via a unique ring cleavage reaction and subsequent reductive treatment of dithiines 497 proceeds to give 2,3-dihydrothieno[3,4-/ ]thiophenes 498 and 499. Heating of 499 in the presence of further iodomethane leads to the formation of the thieno[3,4-/ ]-thiophenes 500 (Scheme 63). 

Being formally a derivative of carbonic acid, 4,5-bis(ethylenedithio)-l,3-dithiol-2-one 188 is opened into the dipotassium salt 192 by the action of potassium ethoxide in THF (Equation 20) <1974JOC511>. 

A very elegant, simple, versatile and high yielding synthesis of fused l,3-dithiol-2-ones has been described recently. In a representative example, treatment of 4-benzoyloxy-l-bromo-2-butyne with potassium O-methyl xanthate in methanol gave the expected xanthate ester in excellent yield. Refluxing of this ester in chlorobenzene for one hour in the presence of dimethyl fumarate gave 1 in quantitative yield. 

Several complexes between tin(rv) centers and the l,3-dithiole-2-thione-4,5-dithiolato or l,3-dithiole-2-one-4,5-dithiolato ligands have been prepared by Wardel s group by methathesis reactions involving addition, elimination, and substitution at the metal atom (Scheme 5) C1998POL4475, 1999JOM140>. 

A simple method for the preparation of l,3-dithiol-2-ones 196 using radical methodology has been reported [95CC1429]. The reaction involves heating of diisopropyl xanthogen disulfide 193 with a terminal alkyne at 80 °C in the presence of a radical initiator. The reaction conditions are compatible with a variety of functional groups on the alkyne. 

Reviews have appeared on benzo-l,3-dithioles, -diselenoles and -ditelluroles [93SR103], the organic chemistry of l,3-dithiol-2-one-4,5-dithiolate ("DMIT") [95S215], and various... 

Quantum mechanical calculations for the 1,3-dithiolylium ion, benzo-1,3-dithiolylium ion, l,3-dithiol-2-one and l,3-dithiole-2-thione have been carried out with the simple LCAO MO method <66AHC(7)39). According to these calculations, the lowest electron density was found at the 2-position of the 1,3-dithiolylium cation, and the C(4)—C(5) bond order corresponded approximately to that of an isolated C—C double bond. A delocalization energy of 105 kJ mol-1 has been calculated for this cation. For the benzo-l,3-dithiolylium ion it was found that nucleophilic attack should take place in the 2-position but electrophilic substitution at the 4-position. 

This section is divided into reactions of fully unsaturated rings like 1,3-dithiolylium ions, mesoionic 1,3-dithiolones, l,3-dithiol-2-ones and l,3-dithiole-2-thiones, and reactions of the saturated 1,3-dithiolanes. As a consequence of the positive charge in 1,3-dithiolylium ions, the main reactions of this class of compounds consist of nucleophilic attack at the 2-position, whereas the mesoionic 1,3-dithiolones undergo cycloaddition reactions. Reactivity of the benzo ring in benzo-l,3-dithiole and related systems has not been studied to any extent. 

A photochemical decarbonylation reaction has been observed with the l,3-dithiol-2-one... 

In the presence of acid, / -thioxodithiocarbonates (249) cyclize to produce l,3-dithiol-2-one derivatives (250) in fair yields (76S489). 

Another preparation of differently substituted l,3-dithiol-2-ones starts from the unsaturated dithiocarbonates (251) which on treatment with iodine lead to the dithiolanone derivatives (253) via the salts (252). Abstraction of hydrogen iodide from (253) gives (254) and subsequent treatment with trifluoroacetic acid yields the l,3-dithiol-2-ones (255 Table 11). The entire reaction sequence can be easily performed in a few hours (80JOC2959). 

Table 11 Yields of l,3-Dithiol-2-ones (255) Synthesized from Unsaturated Dithiocarbonates (251) (80JOC2959)...

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