2.3- Dihydro-l,4-dithiins

The stereospecific formation of 5,6-dihydro-l,4-dithiins from the reaction of the 13-dithiete 60 with alkenes has been shown to proceed through its valence isomer, l,2-bis(methoxycarbonyl)ethane-13-dithione (Scheme 42) <99JOC8489>. 

Evidence of the existence of oxidation state +IV is not yet convincing. Some complexes with dithiolene or dithiolate systems have been reported, such as [Au(5,6-dihydro-l,4-dithiin-2,3-dithiolate)2] (Figure 1.76) [350], or [Au(2,3-dithiophe-nedithiolate)2] [351]. They were prepared by chemical or electrochemical oxidation of... 

TMPD = A/,Ai,Ai, Ai -tetramethyl-p-phenylenediamine PTZ = phenothiazine POZ = pbenoxazine TRP = tropylium cmt = c -l,2-dicarbomethoxyethylenedithiolato DDDT = 5,6-dihydro-l,4-dithiin-2,3-dithiolato. 

Dihydro-l,4-oxathiins 481 (Z = 0) and 5,6-dihydro-l,4-dithiins 481 (Z = S) are easily obtained from 1,3-oxathio-lanes 480 (Z = O) and 1,3-dithiolanes 480 (Z = S), respectively (Scheme 223), by treatment with bromine <1991S223>, TV-bromosuccinimide <1994T7265>, or chlorine <1987JOC5374, 1991S223>. 

The expansion of the ir-conjugating system with outer heterorings, the idea presented by the ET molecule, can be applied to 1,2-dithiolene metal complexes with the donor character. For example, the M(dddt)2 (dddt=5,6-dihydro-l,4-dithiin-2,3-dithiol M = Ni, Pd, Pt, Au) molecule, where the central C = C double bond in ET is replaced by the transition metal, exhibits various molecular arrangements, some of which are similar to those found in the ET salts [29]. In the frontier molecular orbital of the 1,2-dithiolene complexes, the 3p orbitals of S atoms in the ligand show a significant contribution. In this sense, the molecular design for the 1,2-dithiolene complexes can be discussed in common with that for the organic ir molecules. 

In contrast to anionic [M(dmit)2] acceptor molecules, the metal complexes with dddt ligands, [M(dddt)2] (dddt = 5,6-dihydro-l,4-dithiin-... 

An interesting feature concerning the redox properties of the complex, [Au(dddt)2] (dddt = 5,6-dihydro-l,4-dithiine-2,3-dithiolate, 3), is that the one-electron oxidized product, [Au(dddt)2]°, can be isolated14. An X-ray analysis of the neutral complex reveals a square planar gold structure stacked in dimeric units as a result of intermolecular S-----S contacts. Extended Hlickel calculations predict that the odd electron resides pri-... 

Dihydro-l,4-dithiin-2,3-dithiolate Centrid Nitride Azide... 

Although the formation of dithioacetals generally is a simple reaction, side reactions become prevalent when a reasonable leaving group is in the a-position to the carbonyl or to a conjugated double bond. In the reaction of 2-bromo-2-phenylacetophenone with ethanedithiol, 2,3-diphenyl-5,6 dihydro-l,4-dithiin (equation 8) was obtained . Similarly, the dihydro-dithiin (1) was obtained from 6-j3-acetoxy 4-cholesten-3-one (equation 9 f, Additional examples exist for the formation of dihydro-1,4-dithiins via halides , epoxides and even amides . 

DIHYDRO-l,4-DITHIIN-2-YL)METHANOL NOT SIMPLY A HOMOLOGATING AGENT... 

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