Thietane

The thermochemically determined strain enthalpy of thietane is only 80 kj mol . The activation energy for the ring inversion was found spectroscopically to be 3.28 kJ moP and hes above the four lowest vibration levels. The ring is thus not planar  

The reactivity of thietanes toward nucleophiles is much less than that of thiiranes. For instance, thietane does not react with ammonia or amines at room temperature. Electrophiles attack the S-atom and can thereby cause ring-opening. Thus, addition of acids leads to polymerization. A further example is their ring-opening by haloalkanes  

This demonstrates again that a positive charge on the heteroatom destabilizes the ring. Hydrogen peroxide or peroxy acids oxidize thietanes to 1,1-dioxides (cyclic sulfones) via 1-oxides  

Thietanes can be prepared from y-halo thiols or 1,3-dihaloalkanes as follows (1) Cyclization of y-halo thiols or their acetyl derivatives by bases 

Better yields are obtained from (3-chloropropyl)isothiouronium bromide, which is prepared from thiourea and l-bromo-3-chloropropane the latter is available by addition of hydrogen bromide to aUyl chloride  

Oxetanes rarely occur in nature. The diterpene alcohol taxol (paclitaxel ) was isolated in 1971 from the bark of the pacific yew tree (Taxus brevifolia) native to the northwest USA, and its structure elucidated. The compound, which is now marketed, contains an oxetane ring and displays a strong antitumour and antileukaemia activity. Its total synthesis has been achieved [5]. 

This demonstrates again that a positive charge on the heteroatom destabilizes the ring. 

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Although no consistently effective chemical repellent has been developed for vertebrate pests, some promising materials have been tested as repellents that are based on predator avoidance, specifically compounds from the secretions of predators. In 1995, synthetic sulfur compounds (two thietanes, a thiolane, and a substituted methyl sulfide, which were originally identified from the anal glands of the stoat, ferret, and red fox) suppressed browsing by the introduced AustraUan bmsh-tail opossum in New Zealand about as well as FEP (83). Suggestions were made that these compounds can be made more effective by the use of bitter compounds in a cocktail. 

Electron deficient species can attack the unshared electron pairs of heteroatoms, to form ylides, such as in the reaction of thietane with bis(methoxycarbonyl)carbene. The S —C ylide rearranges to 2,2-bis(methoxycarbonyl)thiolane (Section 5.14.3.10.1). A"-Ethoxycar-bonylazepine, however, is attacked by dichlorocarbene at the C=C double bonds, with formation of the trans tris-homo compound (Section 5.16.3.7). 

The salts of -halo acids cyclize in ionizing media to oxetan-2-ones, as do -diazonium carboxylates (64HC(19-2)787). Thietanes are obtained analogously (Section... 

Many [2 + 2] photocycloadditions have not been assigned a definitive mechanism, but they serve well as synthetic methods. Thiones add vinyl ethers to give thietanes in very good yields (Section 5.14.4.1.2), and interesting wavelength-stereochemistry relations were found in the photoaddition of 2-adamantanone to dicyanoethylene (Section 5.14.4.1.2). Diheterocyclobutanes can also be prepared by [2 + 2] photocycloadditions (Section 5.13.3.3). 

A few special syntheses of thiirane derivatives from four-membered sulfur heterocycles are known. Methylenethiiranes are derived by thermolysis of the tosylhydrazones of thietan-3-ones (Scheme 143) (81TL4815), and 2,2,3,3-tetrakis(trifluoromethyl)thiirane is obtained by thermolysis of 2,2,4,4-tetrakis(trifluoromethyl)-l,3-dithietane 1,1-dioxide with loss of sulfur dioxide. 2,2,3,3-Tetrakis(trifluoromethyl)thiirane 1,1-dioxide is obtained in low yield by heating a mixture of 3,3-bis(trifluoromethyl)-l,2,4-oxadithietane 2,2,4,4-tetroxide and bis(trifluoromethyl)ketene. The mono-episulfide of norbornadiene is obtained from thietane derivative (65 Scheme 144) (73JOC649). 

A -Thietane 1-oxide, 3-methyl- C NMR, 7, 414 (820MR(18)82, 80UP51401) 1A -Thietane 1-oxide, 3-methyl-3-phenyl- C NMR, 7, 414 (80JOC4807)... 

NMR, 7, 409 Thietane, 2-thioxo-rearrangements, 7, 422 Thietane, triimino-cycloadducts, 7, 433 synthesis, 7, 41 Thietane-2,4-diones synthesis, 7, 435 Thietanes, 7, 403-447 5-amination, 7, 444 basicity, 7, 424 bicyclic... 

B. 3-Chlorothietane 1,1-dioxide. Thietane 1,1-dioxide (14.0 g, 0.132 mol) is placed in a three-necked, 500-mL, round-bottomed flask fitted with a magnetic stirrer, reflux condenser and a chlorine bubbler, caution sinae ahtovine is poisonous, the reaation involving it should be done in a good hood.) Carbon tetrachloride (300 mL) is added to the flask (Note 4) and the suspension is irradiated by a 250-watt sunlamp positioned as close as possible to the reaction flask without touching it (Note 5) while chlorine is bubbled through the solution for 15 min at a moderate rate (Note 6). A copious white precipitate forms and irradiation and addition of chlorine must be stopped at... 

D. 3,3-Diahlarothietane 1,1-dioxide. Thietane 1,1-dioxide (5.0 g, 0.047 mol) Is placed In a 500-mL, three-necked, round-bottomed flask equipped with a reflux condenser, magnetic stirrer, and chlorine gas bubbler. Carbon tetrachloride (350 mL) Is added and the solution Is irradiated with a 250-watt sunlamp (Note 5) while chlorine Is bubbled through the stirred mixture for 1 hr (Note 9). Irradiation and chlorine addition are stopped and the reaction mixture is allowed to cool to room temperature. The product Is collected by filtration as a white solid (4.0-4.4 g, 49-53%), mp 156-158°C (Note 10). The product can be used without further purification or It can be recrystallized from chloroform. 

Selective chlorination of the 3-position of thietane 1,1-dioxide may be a consequence of hydrogen atom abstraction by a chlorine atom. Such reactions of chlorine atoms are believed to be influenced by polar effects, preferential hydrogen abstraction occurring remotely from an electron withdrawing group. The free radical chain reaction may be propagated by attack of the 3-thietanyl 1,1-dioxide radical on molecular chlorine. 

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