1.3- Dithiolan-2-ones

Ethanedithiol and phosgene react in ether at room temperature to produce the 1,3-dithiolan-2-one (293) in 83% yield (41RTC453). This is probably the best synthesis for (293). 

FIGURE 16 Coupling between CS2 and epoxides leading to a variety of S-containing heterocycles (A) l,3-oxathiolane-2-thiones, (B) 1,3-dithiolane-2-ones, (C) l,3-dithiolane-2-thiones, (D) l,3-oxathiolane-2-ones, and (E) thiiranes. 

Catalytic hydrogenation of (4 V,6 / ,9 a5)-4 -phenyl-6 -propylhexahydros-piro[l,3-dithiolane-2,8 (l //)-pyrido[2,l-c][l,4]oxazin]-l -one over Raney Ni in MeOH gave (4V,62 ,9a5)-4-phenyl-6-propylperhydro[2,l-c][l,4]oxazin-l-one (OOJOC4435). 

In the synthesis of l,3-dithiolan-2-ones from spirocyclic intermediates, via episulfides, substituted tetrathiacyclododecane and the related pentathiacyclopentadecane were isolated in good yields <96JCS(P1)289>. Preparation and molecular dynamics studies of 2,5,8,17,20,23-hexathia[9.9]-p-cyclophane have been reported <96P4203>. The syntheses and properties of thiocrowned l,3-dithiole-2-thiones and their conversion to tetrathiafiilvenes via treatment with triethylphosphine have been described <96LA551>. 

Reaction of thiolates with the l,2-dithiolan-3-one 1-oxide heterocycle of leinamycin generates the snlfenate intermediate Cyclization of this sulfenate onto... 

A more complex structure is that of leinamycin 45 (Scheme 15), a material with potent cytotoxic and antitumor properties, isolated from a Streptomyces sp. A 1,2 dithiolane-3-one ring is spiro fused to a complex macrolactam96 (and references therein). Leinamycin has the remarkable ability to cleave DNA. In brief, leinamycin reacts with a thiol and, after a profound rearrangement, forms an episulfonium ion. This ion alkylates the N7 position of guanosine residues in double stranded DNA an unstable adduct is depurinated by hydrolysis of the glycosidic bond between the alkylated base and a deoxyribose residue. Some structurally less complex l,2-dithiolane-3-one 1-oxides have a similar DNA cleaving ability.97... 

The preparation of dithianes from enamines by reaction with trimethylene dithiotosylate (propane-1,3-dithiol di-p-toluenesulfonate) has been applied with enamines derived from oholostan 3 one, aceto-acetic ester, and phenylacetone.6 7 Reactions of trimethylene dithiotosylate with hydroxymethylene derivatives of ketones also give rise to dithianes thus the hydroxymethylene derivative of cholest-4-en-3-one can be converted to 2,2-(trimethylenedithio)cholest-4-en-3-one. 1,3-Dithiolanes are obtained in a similar manner by reaction of ethylene dithiotosylate1 with the appropriately activated substrate.5,7... 

The chemistry of nonaromatic condensed 1,3-dithiolanes has received considerable interest due to the reported interesting conductivity properties. Some of this chemistry has been recently reviewed <1995S215>. The chlorination of 188 was efficiently performed with 1 equiv of SO2CI2 in refluxing carbon tetrachloride to afford racemic 189 with 2 equiv of sulfuryl chloride, /ra r-5,6-dihydro-5,6-dichloro-l,3-dithiolo[4,5-3][l,4]dithiene-2-one 73 was obtained as a racemic mixture of (R,R)- and (3, 31-enantiomers without any (R,31-diastereoisomer, as confirmed by the presence of a single H NMR signal. Dehydrochlorination of 189 and 73 into 190 and 191, respectively, could be effected as shown in Scheme 9 <2000CC1117>. 

As another important mechanistic type, fragmentation into at least three products that are formed more or less simultaneously has to be mentioned. Such [5 - 2 + 2 + 1] reactions were encountered in 2-pyrrolidinones (65, 67), certain pyrazolidine derivatives (68, 72, 73), l,2,4-triazolidine-3-ones (69) and l,2,4-triazolidine-3,5-diones (70), 2//-pyrrol-2-ones (71), 1,3-dithiolane 1-oxides (78), 1,2,3,4-thiatriazoles (74), 1,2,4-oxadiazolines (75), and in several rings containing sulfur in an oxidized state (76-79,82). Most of these molecules have an exocyclic double bond. 

The 8 + 2-cycloaddition of 2//-cy c I o h cpta[h ] furan -2 - one (155) with acyclic 1,3-dienes provides a facile route to bicyclo[5.3.0] ring systems (156) (Scheme 61).291 2H-Benzo[Z>]thiete in the o-quinoid form undergoes 8 + 2-cycloaddition with 1,3-dithiolane-2-thione, l,3-dithiole-2-thiones, and adamantanethione to produce 4//-1,3-benzoditliianes.292... 

The 7-(5-amino-l,3-dithiolan-2-ylidene)-3-phenyl-5,6,7,8-tetrahydro[l,2,4]triazolo[3,4-A][l,3,4]thiadiazepin-6,8-dione 105 was obtained through the intermediate M by treating 98 with CS2 and chloroacetonitrile in a one-pot reaction under PTC (DMF/K2CO3/TBAB) (Scheme 10). 

The 1,3-dipolar cycloaddition of the carbonyl ylide (31) to the aldimine (32) produces the adduct (33), which has been used to synthesize the taxol C(13) side-chain (34), which is known to be required for the antitumour activity of taxol (Scheme 9).35 The dirhodium tetraacetate-catalysed decomposition of l-diazo-5-phenylpentane-2,5-dione (35) yields the carbonyl ylide (36), which cycloadds to methylenecyclopropanes (37) to produce spirocyclopropanated 8-oxabicyclo[3.2.1]octan-2-ones [(38)-(40)] in 6-75% yields (Scheme 10).36 The 1,3-dipolar cycloadditions of aliphatic or alicyclic thiocarbonyl ylides with thiobenzophenone produce both regioisomeric 1,3-dithiolanes as expected. However, in the case of highly sterically hindered thiocarbonyl ylides, methylene transfer leads to the formation of 4,4,5,5-tetraphenyl-l,3-dithiolane.37,38... 

The extension of the use of lactams to include indolin-2-ones provides a Vilsmeier-type methodology for the construction of biindolyl systems, which are of considerable current interest.37,39-43 In this situation, the initially formed imines are indolenines, which readily isomerize to the related 2-indolyl derivatives.43 In view of our general interest in activated indoles, as well as a specific interest in continuing to synthesize structures containing indoles directly linked to each other, we investigated not only reactions with indolinone itself but also with substituted derivatives. These were variously methoxy-substituted at C-4 and C-6, and in some cases substituted also at C-3 with methyl, phenyl, or dithiolan groups. 

As the final pH of meat increases above the normal range of 5.6-5.8, there is a decrease in meat flavour.101102 The reaction between norfuraneol and cysteine, which plays a crucial role in meat flavour, is very sensitive to pH.103 At pH 4.5, the major volatile products are mercaptoketones, furan- and thiophenethiols, 2-methyltetra-hydrothiophenone, and 3,5-dimethyl-l,2-dithiolan-4-one, whereas, at pH 6.5, these compounds were detected, if at all, only in traces, except for the thiophenone however, pyrroles, pyrazines, thiazoles, and oxazoles had achieved prominence. The sensory observations are a clear reflection of such differences. Similar effects of pH had been found for the ribose-cysteine and other systems.104... 

The selective Bock Oxidation using AICI3/CH2Q2 in the meantime has formed widespread application for main group element compounds the prediction of one-electron oxidizability based on first ionization energies IEJ < 8 eV is valid also for numerous other classes of compounds. For examples of ESR/ENDOR-detected radical cations or their rearrangement products, see BN heterocycles H. Noth, W. Winterstein, W. Kaim and H. Bock, Chem. Ber., 112, 2494 (1979) tetra-teri-butyltetrahedrane H. Bock, R. Roth and G. Maier, Chem. Ber., 117, 172 (1984) tetrakis(dimethylamino)-p-benzoquinone H. Bock, P. Hanel and U. Lechner-Knoblauch, Tetrahedron Lett., 26, 5155 (1985) 1,2-dithiolane H. Bock, B. I. Chenards, P. Rittmeyer and U. Stein, Z. Naturforsch. B, 43, 177 (1988), and references cited therein. 

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