Thietes reactions

C. Thiete 1,1-dioxide. A sample of 3-chlorothietane l,l-d1ox1de (8.0 g, 0.057 mol) Is dissolved In dry toluene (300 ml) (Note 7) In a 500-mL, twonecked, round-bottomed flask equipped with a reflux condenser, magnetic stirrer, heating mantle (or silicone oil bath), and thermometer. The reaction Is heated to 60° C and tri ethyl amine (28.7 g, 0.28 mol, 39,5 ml) Is added through the condenser. The reaction mixture Is stirred for 4 hr and triethyl-amine hydrochloride is removed by filtration and washed with toluene (100 mL), Toluene is removed on a rotary evaporator and the residue is recrystallized from diethyl ether-ethanol (Note 8) to give a white solid (4.5-4.8 g, 75-81 ) mp 49-50°C (llt mp 52-54°C). 

The following compounds have been obtained from thiete 1,1-dioxide Substituted cycloheptatrienes, benzyl o-toluenethiosulfinate, pyrazoles, - naphthothiete 1,1-dioxides, and 3-subst1tuted thietane 1,1-dioxides.It is a dienophile in Diels-Alder reactions and undergoes cycloadditions with enamines, dienamines, and ynamines. Thiete 1,1-dioxide is a source of the novel intermediate, vinylsulfene (CH2=CHCH=SQ2). which undergoes cyclo-additions to strained olefinic double bonds, reacts with phenol to give allyl sulfonate derivatives or cyclizes unimolecularly to give an unsaturated sultene. - Platinum and iron complexes of thiete 1,1-dioxide have been reported. 

Chloroth1ete 1,1-dioxide is a potentially useful intermediate for the preparation of other 3-substituted thiete 1,1-dioxides via addition-elimination reactions. 

Base-induced eliminative ring fission, in which both the double bond and the sulfone function take part, has been observed in thiete dioxides253. The reaction can be rationalized in terms of initial Michael-type addition to the double bond of the ring vinyl sulfone, followed by a reverse aldol condensation with ring opening. The isolation of the ether 270c in the treatment of 6c with potassium ethoxide (since the transformation 267 -> 268 is not possible in this case) is in agreement with the reaction mechanism outlined in equation 101253. 

As expected, 1 1 (2 + 2) cycloadducts are obtained in the reactions of thiete dioxides with some typical electron-rich olefins, e.g. enamines and ynamines, although this cycloaddition has not proven to be general190. 

Dittmer and Christy64 studied the reactions of thiete sulphone. Included in these was an attempt to synthesize thiete itself, a highly strained olefin of theoretical interest, by the LAH reduction of thiete sulphone. The reduction was expected to be feasible since Bordwell and McKellin63 had found that thietane sulphone was readily reduced, but the only product that Dittmer and Christy isolated was 1-propanethiol (equation 23). Reduction of the thiete sulphone with sodium borohydride in basic aqueous methanol gave a 61% yield of the saturated ring, thietane sulphone. 

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. 

The preparation and investigation of the thietane oxide system (5a) is largely associated with stereochemical and conformational studies . The investigation of the thietane dioxides (5b) is substantially related to the chemistry of sulfenes , the [2 -I- 2] cycloaddition of which with enamines is probably the method of choice for the synthesis of 5b . The study of the thiete dioxide system (6) evolved, at least in part, from the recognition that the unstable thiete system 183 can be uniquely stabilized when the sulfur in the system is transformed into the corresponding sulfone , and that the thiete dioxide system is very useful in cycloadditions and thermolytic reactions. The main interest in the dithietane oxides and dioxides (7) appears to lie in the synthetic challenge associated with their preparation, as well as in their unique structural features and chemical behavior under thermolytic conditions . ... 

The formation of cyclic sulfinic esters (sultines) from vinyl sulfenes is known , and the trapping of the expected intermediate vinyl sulfene in the thermolysis of thiete dioxide (6fc and 194) has been convincingly achieved . Specifically, thermolysis of thiete dioxide 6b in the presence of norbornenes gave cycloadducts of the Diels-Alder type (i.e. 252b), resulting from the trapping of the vinyl sulfene formed. The accumulated evidence thus supports the proposed mechanism for these thermolytic reactions. 

It is intriguing to note that this reaction scheme for the reduction of a sulphone to a sulphide leads to the same reaction stoichiometry as proposed originally by Bordwell in 1951. Which of the three reaction pathways predominates will depend on the relative activation barriers for each process in any given molecule. All are known. Process (1) is preferred in somewhat strained cyclic sulphones (equations 22 and 24), process (2) occurs in the strained naphtho[l, 8-hc]thiete 1,1-dioxide, 2, cleavage of which leads to a reasonably stabilized aryl carbanion (equation 29) and process (3) occurs in unstrained sulphones, as outlined in equations (26) to (28). Examples of other nucleophiles attacking strained sulphones are in fact known. For instance, the very strained sulphone, 2, is cleaved by hydride from LAH, by methyllithium in ether at 20°, by sodium hydroxide in refluxing aqueous dioxane, and by lithium anilide in ether/THF at room temperature. In each case, the product resulted from a nucleophilic attack at the sulphonyl sulphur atom. Other examples of this process include the attack of hydroxide ion on highly strained thiirene S, S-dioxides , and an attack on norbornadienyl sulphone by methyllithium in ice-cold THF . ... 

The reaction of Af,Af-dimethyl-( )-styrylamine (73) with a halogen-substituted methanesulfonyl chloride allowed the first stereoselective formation of the halogenated thietane 1,1-dioxide 74, which then could be converted to the corresponding thiete sulfone 75 via a Cope elimination of the corresponding AT-oxide. ... 

The oxides of thiete and benzothiete have been prepared from halogenated thietane oxides by elimination reactions. (Eqs. 25 and 26)... 

The susceptibility of the thiete 1,1-dioxides to nucleophilic addition reactions can be utilized to produce 3-substituted thietane derivatives. For example, the thus easily attainable 3-cyano and 3-nitroalkyl-substituted derivatives could be reduced to the 3-aminomethylthietanes ° (Eq. 61). 

Thiete sulfones show an irregular behavior pattern when involved in cycloaddition reactions. With 1,3-dienes, dienamines, enamines, ynamines, diazoalkenes, cyclopropadiene, and its substitution products, furan, and anthracene, the addition proceeds in the normal fashion. With certain Diels-Alder reagents such as tetraphenylcyclopentadienone (tetracycloneX however, the cyclic sulfones react anomalously. The Diels-Alder adducts undergo decomposition with SO 2 and CO extrusion to a seven-membered ring, the tetraphenylcycloheptatriene 223. Bicyclic octadienone is produced as well (Eq. 62). The mechanism of this unusual reaction is proposed by... 

Dittmer et al. to be as shown in Scheme 13. The final product 223 resulting from intermediate 224 via CO expulsion and subsequent proton rearrangement is more likely than the reverse-reaction sequence. Thiete 1,1-dioxide... 

Reaction of thiete and its fused derivatives with alkyllithium and alkyl-potassium bases leads to the opening of the ring via two different modes of cleavage. (Scheme 14)... 

Thiete can undergo a ring-opening reaction with trityllithium or potassium mesylate (Scheme 15). 

Fused thietes often show a different chemical behavior than the thietes themselves. The fused thiete undergoes ring opening much more readily because of greater ring strain, and thus the reaction with 2,4-dinitrophenyl-hydrazine takes a different course (Schemes 15 and 16). 

X-Ray analysis of the red-orange crystalline thioacrolein complex 272, which is derived from the dimeric thioacrolein derivative by way of thermal elimination of carbon monoxide (Scheme 17), has revealed a structure with an essentially square FejSs array. Analogous reactions with iron carbonyls have been carried out by McCaskie et who used thiete 1,1-dioxide instead of thiete (Scheme 18). 

Flash vacuum pyrolysis has been used in the synthesis of 2ff-naphtho[l,2-f>]thiete 8 <98JHC1505> and benzobisthietes 9 and 10 <98TL9639>, and their Diels-Alder cycloaddition reactions have been studied. 

Scheme 1 summarizes some of the common electron-impact induced fragmentation pathways available to thietanes, thietes and their 5-oxides. Major processes include retro-2 + 2 fragmentation for thietanes, thiolactones and iminothietanes, loss of sulfur oxides for thietane 5-oxides, and loss of an a-hydrogen atom from thietes and benzothietes. Certain of these processes, considered to involve electron-impact induced pathways, may actually involve thermolytic reactions occurring in the source region of the mass spectrometer (78JHC421,71JA676). 

Examples of reactions of the carbon-carbon double bond of thietes with protic acids are... 

Oxygen can be introduced into the a-positions of thietanes by treatment of the thietane with lead tetraacetate as in the formation of (204) (75JOC3046). Thietanones can be prepared by hydrolysis of thiete enamines such as (205) (65LA(684)103) or by oxidation of 3-thietanol with DMSO/benzoic anhydride (78PS(4)167>. Thietanones can be converted into various ring-substituted sulfur derivatives as already illustrated in reactions of (68) and preparation of (199). 

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