Thietes with nucleophiles

The simple thietes are unstable with respect to treatment with strong bases or nucleophiles. Proton abstraction from thiete was observed via deuterium-proton exchange with CH3OD-CH3O it appeared to be faster than exchange with allyl sulfide, but slower than that with phenylacetylene. " The thiete, however, could not be recovered from the reaction mixture. Treatment of thiete with potassium t-butoxide did not result in incorporation of deuterium when the reaction was quenched with D2O treatment with potassium 1-methylcyclohexoxide resulted in the rapid disappearance of the nmr absorption of the protons of the thiete. ... 

Electrophilic sulfenes, R2CMSO2, are recognized for their ability to react with nucleophiles and for their 2ir participation in [2 + 2] and [4 + 2] cycloadditions (Chapter 5). Less well recognized is the demonstrated 4ir participation of vinyl sulfenes in Diels-Alder reactions with a select set of dienophiles. Thermolysis of thiete 1,1-dioxides including the parent thiete 1,1-dioxide (22) in the presence of norbornenes provided the Diels-Alder products derived from 4w participation of the vinyl sulfenes [Eq. (18)].40... 

Meinwald and coworkers71 studied the chemistry of naphtho[l, 8-bc]thiete and its S-oxides. The reaction of the sulphone 2 with LAH (equation 29) is of particular and direct relevance to this section since it is different from the reductions that have been discussed thus far, because the major reaction pathway is now cleavage of an S—C bond, rather than a deoxygenation of the sulphur atom. The major product (equation 29) was isolated in 65% yield two minor products accounted for a further 15% yield. One of the minor products is 1-methylthionaphthalene and this was most probably produced by an initial reduction of the strained 1,8-naphthosulphone, 2, to the thiete, which was then cleaved to the thiol and subsequently methylated. Meinwald also showed71 that the thiete was subject to cleavage by LAH as well as that both molecules were susceptible to attack and cleavage by other nucleophiles, notably methyllithium. These reactions are in fact very useful in attempts to assess a probable mechanism for the reduction of sulphones by LAH and this will be discussed at the end of this section. 

It was assumed (90JFC(48)133, 87IZY957) that perfluoro-2,4,4-trimethyl-3-isopropyl-2-thiete 28 is produced by the reaction of isomeric perfluoro-3-isopropyl-2-methyl-2-pentene with tert-butylmercaptan in the presence of triethylamine, which takes place by intramolecular cyclization of the S-nucleophile at the carbon atom of the CF fragment. 

Methyllithium attacked the sulfur atom of naphthothiete 205 to give 231 and oligomers 232 and 233 via 8-mercaptomethyl-l-lithionaphthalene. Treatment with lithium aluminum hydride followed by methylation gave 234. Treatment of thiete 215 with triphenylphosphine leads to ring-expanded products possibly via nucleophilic attack by phosphorus on sulfur. ... 

Additions of the Michael type of nucleophiles to the carbon-carbon double bond of thiete 1,1-dioxides to give 3-substituted thietane 1,1-dioxides occur readily. The addition of hydrogen has been discussed in Section A. Nucleophiles include cyanide, the anion of nitroethane, the lithium salt of r-butyl o-tolyl sulfone, dimethylamine, cyclohexylamine, ethoxide, and hydrogen sulfide. The reaction is exemplified by the synthesis of 278. Additions to 3-chloro-2H-thiete 1,1-dioxide most likely proceed by an addition-elimination mechanism an example is shown for the addition of the anion of dimethylmalonate to give 279. The replacement of a 3-morpholinyl group by a 3-A methyl-A-phenylamino group in thiete 1,1-dioxide is another example of addition-elimination. An addition of ethoxide with elimination of p-nitrophenyl anion may occur with 268 (Ar = / -N02C6H4). " Addition of bromine via N-bromo-succinimide to the double bond of 4-phenyl-2H-thiete 1,1-dioxide occurs only in 1.5% yield. ... 

Refluxing 2,4-diphenyl-2H-thiete 1,1-dioxide in ethanol yields the acyclic sulfone 286. Treatment of naphthothiete sulfone 205b with methyllithium, sodium hydroxide, or lithium anilide gives products, for example, 287, resulting from nucleophilic attack on the sulfur atom of the sulfone... 

The thietane ring of the carboxylate derivative 352 is apparently opened by loss of carbon dioxide. possibly via a thiete intermediate. Isonitriles and ynamines effect ring-expansions of 2,4-bis(imino)thietanes, and similar reactions of enamines and ynamines with tris(imino)thietane, 353 have been reported. The nucleophiles — methanol, ethanethiol, and diethylamine — attack the a-carbon atom of 353, which bears the iminosulfonyl group, to give ring-opened products, for example, 353a. The reactions with sodium azide or hydrazoic acid take a different course. ... 

The reaction of naphthosulfone (36, Scheme 11) with the lithium aluminum hydride takes two directions. The first route consists in reduction to naphthothiete (34) with subsequent transformations represented in Scheme 10 (34—>56—>57—>58 59) on quenching dilithium intermediate 57 with water (R = H). The second path involves opening the hetero ring with the nucleophile without reduction (36—>65 67) also analogous to (34 -> -> -> 59) for naphtho[l,8-Z c]thiete proper (cf. Schemes 10 and 11). Methyl naphthyl sulfone (67) thus obtained was also prepared by an independent synthesis by treating naphtho[l,8-Z c]sulfone (36) with methyllithium followed by quenching with water (36 66—>67). 

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