4.4.5.5- Tetramethyl-1,2-dithiane

The complexes of tetramethyl- and tetraethyl-dithio-oxamide have been investigated by the Job method, and [FeLjX ] (X = CIO or FeClJ were identified. The i.r. spectrum of [Fe(TMSO) ] is very similar to that of the DMSO analogue. 1,4-Dithiane monosulphoxide forms the complexes [FeX lDTMSOlJ (X = Cl. Br, I. NO3. or NCS = 2, 3, or 6). ... 

Tetramethyl-2,3-digerma-l,4-dithiane (403) decomposes with extrusion of dimethyl-germylene very slowly at room temperature but readily on thermolysis or photolysis to yield 2,2-dimethyl-l,3,2-dithiagermolane (404) <84JOM(277)323>. 

Both the measured dipole moments and H NMR spectra of 1,2-dithiane, its 4,4,5,5-tetradeutero analog, 3,3,6,6-tetramethyl-l,2-dithiane, and the m//ra r-isomers of 3,6-dimethyl-l,2-dithiane provided unequivocal evidence for the chair conformation adopted by the saturated six-membered ring, supported further by X-ray solid-state structures. Other conformers, for example the twist conformer, were not detected . 

As expected, 2-halo-l,3-dithianes react with nucleophiles under Sn conditions. Suitable nucleophiles are enamines <2002TL9517, 2004T6931> and phenols <1997MOL7>. The reaction with EtOC(S)S K, followed by oxidation, provided a xanthate which generated a 1,3-dithiane 1-oxide radical upon treatment with Bu3SnH (Scheme 69) <2004T7781>. An efficient one-carbon radical precursor has also been obtained by addition of 2,2,6,6-tetramethyl-piperidine-l-oxyl (TEMPO) to 2-lithio-l,3-dithiane. The reactivity of this compound has been demonstrated <2005S1389>. 

Under other conditions,9 aldehydes give dimers and even tetramers. The tetramer of acetaldehyde, made by the action of a trace of acid at about 0°, has been shown by X-ray diffraction analysis to be tetramethyl-tetraoxacyclooctane (2).10 The acid-catalyzed dimerization of mercapto-aeetaldehyde acetal HSCH2CH(OEt)2 gives 2,5-diethoxy-l,4-dithian (3), which can be converted to 1,4-dithiadiene by heating at 300° over alumina.11... 

Photolysis of the bicyclic enone 57 gives a modest yield of thietane thermolysis of 5-cyano-2,2,4,4-tetraphenyl-l,3-dithiane gives 3-cyano-2,2-diphenyl-thietane by loss of thiobenzophenone. Photolysis of 3,3,6,6-tetramethyl-S-acetoxy-l-thiacycloheptan-4-one gives a small amount of 3,3-dimethyl-2-acetoxy-thietane which also can be obtained in 30% yield by treatment of 3,3-dimethyl-thietane with lead tetraacetate in pyridine. ... 

The availability of f j-di-r-butyl disulfide monoxide from selective oxidation catalyzed by vanadyl-88 enables the preparation of chiral r-butyl sulfinamides, sulfoxides, and sulfinimines. Very similar reaction conditions bring about the transformation of various 1,3-dithianes to chiral monoxides. (/ ,Rl-2,2,5,5-Tetramethyl-3,4-hexanediol is a chiral ligand for the Ti(IV)-catalyzed oxidation of sulfides with cumene hydroperoxide. ... 

ALDEHYDES 9-Borabicyclo[3.3.1]-nonane. Diazoacetaldehyde. Diethyl-allylthiome thylphosphonate, Diethyl phenyl orthoformate Dithiane. Lith-ium-Alkylamine. Lithium diisopropyl-amide. Sodium tetracarbonylferrate-(TI). 1,1,3,3-Tetramethylbutylisonitrile. 2,4,4,6-Tetramethyl-5,6-dihydro-l, 3-(4H)-oxazine. Triethylsilane. s-Trithiane. 

Reaction of bis(disilanyl)dithiane 6 with an equimolar amount of Pd(CN-t-Bu)2 in benzene was examined at room temperature. The reaction was completed within 5 min, affording l,l,2,2-tetramethyl-l,2-diphenyldisilane and a four-membered cyclic bis-(organosilyl) complex 7 in 85% yield after isolation by crystallization with pentane (Scheme 5). A crystal structure of 7 exhibited a distorted square planar structure, in which the two silicon atoms in the ring are separated only by 2.61 A. Presumably, the formation of 7 may have arisen from the simultaneous activation of the two Si—Si bonds on palladium, which led to intramolecular metathesis (disproportionation). 

With this information at hand, Juaristi and Cruz-Sdnchez [65] prepared 4,4,5,5-tetramethyl-l,2-dithiane mono-5-oxide (24), the rationale being that the syn-diaxial CH3/S=0 interaction in (24-ax) would produce an equilibrium closer to unity in Scheme 3.38, therefore allowing a more precise determination of the conformational preference of the S=0 group in (24) and, indirectly, in (3). 

S-tetramethyl-l -dithiocylcopentane and 1 -dithiane to be stat to polymerization [125], These conflicting reports probably reflect the differences in the purities of the disulfides. 

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