Thianthrene desulfurization

Chang and co-workers isolated strain Nocardia sp. CYKS2 from a dyeing industry wastewater using DBT as the sole sulfur source [27]. This strain also desulfurized DBT to the same product 2-HBP however, it had broader substrate specificity and was reported to desulfurize thiophenes, sulfides, and disulfides (Table 3) in addition to DBT. However, it did not desulfurize trithiane, thianthrene and 4,4 -thiodiphenol. The desulfurization experiments were conducted in batch with the rate reported as 0.279 mg-sulfur/L dispersion/h for DBT conversion. 

Thianthrene was inert to (COD)2Ni(0) alone, but treatment with 2 mol equivalents of the nickel species in the presence of 2 mol equivalents of bpy converted it into dibenzothiophen (60%) and diphenyl (10%). The active desulfurizing agent was considered to be (bpy)(COD)Ni(0), the requirement for two metal equivalents being that one coordinates a sulfur the other effects rupture of the ring Scheme 8 illustrates this (77JOM51). 

Furthermore, thianthrene react with 2-diazo(fluoroalkyl)acetoacetates under mild conditions in the presence of catalytic Rh2(OAc)4 to afford the corresponding sulfonium ylides as the major products <2004JFC(125)1071>. In addition to all the desulfurization conditions reported in CHEC-II(1996) <1996CHEC-II(6)447>, a new efficient reagent was developed. Introduction of the sodium salt of 3-hydroxy-A-methylpiperidine into the aggregates of NiCRA s (NaH-RONa-NiX2) led to 83% yield of desulfurized thianthrene in 30 min <1998TL8987>. 

Photolysis of these benzynes at 266 nm leads to production of 3,6-difluoro- and 3,6-bis(trifluoromethyl)-l,4-benzdiyne which are converted into the corresponding hexatriynes upon further irradiation at 266 nm. 4,8-Diethylbenzo[l,2-r/ 4,5- ]bis[l,2,3]trithiole 86 undergoes photolytic degradation on irradiation with a high-pressure mercury lamp, without the requirement for an additional desulfurization reagent, to produce thianthrene 87 in low yield (Equation 21) <2000TL1801>. 

The behavior of heterocycles 34, 35, and 36 toward bipy(COD)Ni and was instructive (Scheme 9) here complete desulfurization was the exclusive course, with ring contraction (42) being the preponderant outcome for 34 and 35. Only traces of the hydrodesulfurized product 43 were formed. Thianthrene was converted into dibenzothiophene (33), whose further reactions followed those depicted in Scheme 8. 

A variety of organic sulfur compounds, in addition to DBT, were shown to be substrates for desulfurization by IGTS8, including thianthrene, phenyl sulfoxide, trithiane, and benzyldisulfide. In contrast, IGTS8 could not metabolize thianaph-thene, phenyl disulfide, and 2-thiophene-carboxylic acid (50), a similar substrate profile as the Arthrobacter isolate previously described by Knecht. A number of other bacteria have subsequently been isolated that use an analogous pathway and have similar substrate ranges (51-56). 

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