Thietanes, ring synthesis

A. Roy, B. Achari, and S. B. Mandal, An easy access to spiroannulated glyco-oxetane, -thietane and -azetane rings Synthesis of spironucleosides, Tetrahedron Lett., 47 (2006) 3875—3879. 

With no major research on the reaction of phosphorus ylides and aliphatic or alicyclic thiones prior to their investigation, Krapcho et where able to elaborate a useful method for the synthesis of the thietane ring system in addition to the preparation of novel types of thiocarbonyl stabilized ylides (Eq. 1). 

Workers targeting thietanyl nucleosides via the Pummerer reaction have reported a [3+1] synthesis of thietanose derivatives (i.e., thietane ring-based monosaccharides). Nishizono et al. performed the synthesis of... 

A number of papers describe the synthesis of thietane rings starting from thiirane rings. Lucchini et al. studied the different reactivities of cis and trans di-fert-butylthiiranium ions, 96a and 96b, with water <1997JOC7018>. It was demonstrated that the reaction of cis di-fert-butylthiiranium ion 96a with water led first to the formation of an open-chain alcohol 97, which, after ring closure, formed the trans di-/r y-butylthiiranium ion 96b. The trans Ai-tert-butylthiiranium ion 96b then rearranged to the thietanium ion 98 (Equation 31). 

Several articles within the discussed period were devoted to the synthesis of carbohydrates (mono- and disaccharides) with a fused thietane ring. Cubero et al.< 1996CAR145> synthesized a galactose thietane derivative 72 using sodium methoxide as a condensing agent (Equation 21). 

Oxirane taxol derivatives have also been found to be convenient starting materials for the synthesis of taxols fused with a thietane ring. The oxirane-derived taxine B derivatives 118 and 119 have undergone reaction with potassium thioacetate in dimethylformamide (DMF) at 60°C <2000TL4891, 2001JOC5058>, leading to the formation of thietane-derived taxine B derivatives 57 and 121. In the case of the bromine derivative 118, the thietane-taxol 57 was not the exclusive product and the 1,2-dithiolane derivative 120 occurred as the major product (Equations 35 and 36). 

The thietane ring contraction with bicyclic ylide intermediacy is the basis of the synthesis of thiiradialene 413 by vacuum pyrolysis of tosylhydra-zone lithium salt 414 (81TL4815). 

Although sodium sulphide reacts readily with haloalkanes [2] and activated aryl halides (see Chapter 2) [e.g. 3-5] in the presence of a quaternary ammonium catalyst to form symmetrical thioethers (Table 4.1), a major side reaction results in the formation of disulphides owing to the oxidation of the intermediate thiols under the basic conditions. Consequently, little use has been made of this procedure for the synthesis of thioethers [3, 6], but the corresponding reaction of the a,(0-dihaloalkanes to yield cyclic thioethers has proved to be a valuable procedure for the synthesis of thietanes [7] (Table 4.2). The ring closure with the secondary dihaloalkanes is considerably more difficult to effect than is the reaction of the primary dihaloalkanes. 1,3-Dihydrobenzo[c]thiophene (89%) is produced in the reaction of 1,2-bis(bromomethyl)benzene with sodium sulphide (Scheme 4.1) [8]. The direct... 

Heating of thietanes can often lead to a ring contraction. Thermal treatment (150°C, in vacuo) of the tosylhydrazide salt 213 gives the allene epi-sulfide 214, a unique synthesis for this molecule. The mechanism is suggested to proceed either via the intermediate bicyclobutane ylide 215 or the mesomeric structure 216. Dodson et al. have noticed the rearrangement... 

The reaction of thietanes with electrophilic oxygen will be covered in Section 5.14.4.3 (Synthesis of Derivatives of the Ring Systems). 

Only a limited number of examples are known of applications of thietanes in organic synthesis. Prominent among these examples would be electrophilic ring opening reactions leading to polyfunctional sulfur compounds (33)-(37), utilization of 3-thietanones (55) and metal complexes (87) derived therefrom as oxyallyl zwitterion equivalents in cycloaddition reactions, synthesis of dipeptide (63) with a /3-thiolactone, Raney nickel desulfurization of thietanes (e.g. 120 cf. Table 7) as a route to gem-dimethyl compounds, and desulfurization of thietanes (e.g. 17) in the synthesis of cyclopropanes (also see Table 7). 

Mildly basic to neutral conditions for the ring closure of 1,3-halohydrins include tetra-phenylantimony methoxide as an effective non-basic reagent for oxetane synthesis from 1,3-bromohydrins (90S106). The salts of (3-halo acids cyclize in ionizing media to oxetan-2-ones, as do (3-diazonium carboxylates (64HC(l9-2)787). Thietanes are obtained analogously. 

In the present review the ring systems containing one heteroatom are considered first, except for P-lactams which are given a special section at the end. Interest in azetidines continues to be stimulated by the discovery of the potentially useful trinitro derivative. The requirements for the stereoselective synthesis of substituted oxetane are being explored and derivatives of aluminium are useful in the stereoselective routes to oxetanones. The preparation and subsequent pyrolysis of oxetanones is suggested as an alternative to the Wittig route to olefins. Stereoselective routes to thietanes and thietane 1 -oxides are mentioned. 

This chapter continues this work covering the literature of the last 10 years, that is, from 1996 until 2005. The preparation of this review was based on a literature search through SCOPUS and the Beilstein Database, which revealed 104 important papers published within this period. This chapter is organized in accordance with the general structure of CHEC-III, which includes a division into 12 sections including the same aspects as in CHEC-II(1996). For some aspects of thietane and thiete chemistry, such as their synthesis from six- and seven-membered rings, no new papers were published within the discussed period. 

Padwa et al. <2004JOC33, 20010L1781> established a method for the synthesis of complex fused-ring thietanes by the intramolecular [2+2] photochemical cyclization of thiosuccinimide and dithiosuccinimide derivatives. In the... 

A similar synthesis of tricyclic fused-ring thietanes by photochemical cyclization of N-substituted mono- and dithioglutarimides has been reported (Equations 17 and 18) <2000H(53)2781>. The carbonyl compound 64a and thiocarbonyl derivatives 65 were obtained in moderate yields. An analogous route was used for thiosuccinimides, where the use of a dithioglutarimide derivative resulted in the formation of a bicyclic side product 65. 

Zyk et al. <2000RJ0794> reported the synthesis of fused-ring thietanes by the reaction of the bis-morpholine sulfide-phosphoryl trihalide complex 85 with norbornadiene. The formation of 4-thiatricyclo[3.2.1.03,6]octane 86 was demonstrated and yields varied slightly depending on the phosphoryl trihalide used. When phosphoryl trichloride was used, the yield was 69% in the case of phosphoryl tribromide, it was 72%. The complex 84 was obtained by the reaction of the bis-morpholine sulfide with phosphoryl trihalide in dichloromethane at —40°C (Scheme 15). The same authors <1996RCB2393> performed a similar reaction of norbornadiene with bis-morpholine disulfide-phos-phoryl tribromide complex 87, which led to the formation of the same thietane 86 in 63% yield (Scheme 15). These reactions have also been described by Robin and Rousseau in a review <2002EJ03099>. 

Among the available methods to synthesize fused-ring thietes and bi- or tricyclic thietanes (but not spiro-com-pounds), the most efficient method seems to be the synthesis from acyclic precursors with the same number of carbons. Photocyclization reactions lead to thietes and thietanes in satisfactory to high yields. Mono- and disaccharides bearing fused thietane moieties have been synthesized using this method. 

Alkylation of the sulfur atom of thietane with allyl bromides (or chlorides) gives allyl 3-bromopropyl sulfides, useful intermediates in the synthesis of larger rings, as illustrated by the conversion of thietane to 2-vinylthiolane. ... 

Heating several thietanes with sulfur or selenium yields 1,2-dithiolanes and a 2-selenathiolane, for example, 107 from 19, respectively. The reaction of 108 with sulfur provides a synthesis of thioctic acid. ° A somewhat similar reaction involves heating thietane with aluminum oxide whereby 1,2-dithiolane and hydrogen sulfide are produced, but the dithiolane yield is very low. A photochemical ring-expansion of 99 has been described in Section 11.5.1. ° Treatment of thietane with hexafluoroacetone gives a six-membered cyclic sulfenate. ... 

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