1.3- Benzodithioles, formation

This reaction is essentially thermoneutral. Although we lack enthalpy of formation data for the corresponding 1,3-benzodithiole, the weakness of 1,3 sulfur-sulfur interactions as manifest by the near equality [52] of the enthalpies of formation of 1,3- and 1,4-dithiane (unlike 1,3- and 1,4-dioxane) suggests no special interaction in this nonaromatic heterocycle. Said differently, the thermoneutrality of the above reaction, as opposed to profound exothermicity (21 kJ mol ) for indane (six n electrons) and the endothermicity (29 kJ mol1) for benzimidazolinone (ten n electrons), suggests phenylene trithiocarbonate (ten n electrons) has an intermediate degree of aromaticity. For the latter two species, analysis of the related reactions ... 

Furthermore, the reactions of the benzodithiole (165) with indole derivatives in acetic acid lead to the formation of the substitution products (166). These products can be transformed into the dithiolylium ions (167) by treatment of (166) with trityl tetrafluorobo-rate in acetonitrile. Finally, the cation (167 R1 = H) undergoes deprotonation using triethyl-amine to produce the dibenzo-l,4-dithia-6-azafulvalene (168) (80BCJ1661). 

A general synthesis of a-hydroxy esters is based on 2-ethylthio-l,3-benzodithiole which serves as a methoxycarbonyl anion equivalent. Thus reaction of the lithium compound (216) with ketones followed by treatment with mercury perchlorate in methanol leads to the formation of a-hydroxy acid derivatives (217) (81SC209). 

An approach to nitro-substituted l,3-benzodithiole-2-thiones (325) is based on the reaction of l-chloro-2,6-dinitrobenzenes (323) with sodium f-butyl trithiocarbonate which yields dinitrophenyl f-butyl trithiocarbonates (324). The latter cyclize on heating in acetic acid with formation of nitro-l,3-benzodithiole-2-thiones (325) (80JOC4041). 

Oxidation of tetrathiafulvalenes by Cu(II) salts results in expansion of the benzodithiole ring through cleavage of an S-C(-C) bond and the formation of the 1,4-dithiin ring of a l,4,6,9-tetrathiaspiro[4,5]decane (Scheme 54) <06TL3123>. 

The formation of III and IV can both be understood as a series of addition-elimination reactions occurring on the central C=C bond of I, by the works of sulfur anions liberated by the interaction of o-benzodithiol (II) and trimethyl-amine. However, the direction of the addition reaction cannot be ascertained at first glance, because some confusion may occur if the relative stability of the carbanions resulting from this operation is not carefully analyzed first. For this purpose, there are the handy Baldwin s Rules, although these laws face some problems when applied to second-row elements such as sulfur. Therefore, they will be disregarded here. 

A simple synthesis of symetrically functionalized dithiosalicylides 77a-d from the 377-1,2-benzodithiol-3-ones 75 and triphenylphosphine was described (Scheme 6) <1997JOC9361>. As indicated, the preparation of precursors 75 was based on a known transformation of the substituted anthranilic acid derivatives 73 to the thiosalicylic acid derivatives <1943OSC580>. Upon treatment with thioacetic acid in sulfuric acid, cyclization <1990JOC4693> afforded products 75 in 38-64% yield. Dimerization of a benzothietan-2-one 78a or ketene 78b <1987JOC3838>, arising presumably from initially formed intermediate 76, was proposed to account for the product formation. As revealed... 

Sulfurization of tricoordinated phosphorus compounds by treatment with 3H-1,2-benzodithiol-3-one 1,1-dioxide results from the nucleophilic attack of, for example, a phosphite triester on the electrophilic thiosulfonate function of 2 to produce the phos-phonium sulfinate intermediate 3 (eq 2). Intramolecular condensation of the sulfinate anion with the carbonyl group of the activated thiol ester function releases the phosphorothioate triester (4) with concomitant formation of 5. Because of the... 

However, conversion of the dinucleoside //-phosphonate diester 10 to the phosphorothioate analogue 11 effected by a 0.02 M solution of 2 in 2% aqueous pyridine is relatively slow it reportedly takes 3 h for a complete reaction. While a solution of 2 in 2% aqueous acetonitrile containing triethylamine can completely transform 10 into 11 within 30 s, the use of this sulfurization mixture is incompatible with automated solid-phase oligonucleotide synthesis given the rapid formation of a yellow precipitate caused by triethylamine. In the absence of triethylamine, 10 is not sulfurized under these conditions. Nonetheless, 10 is completely converted to 11 within 20 min when a 0.02 M solution of 1 in 2% aqueous pyridine is used for the sulfurization reaction. Thus, 3i/-l,2-benzodithiol-3-one in aqueous pyridine is compatible with automated solid-phase synthesis of both DNA and RNA oligonucleoside phosphorodithioates or phosphorothioates from appropriate //-phosphonate derivatives. ... 

The introduction of a 1,3-benzodithiol group in a stereoselective fashion can be used to generate an anionic or cationic equivalent and could be easy removed by Raney nickel. This procedure was applied to the synthesis arundic acid [34], which is currently undergoing phase 11 development for the treatment of acute ischemic stroke, and to the bisabolane skeleton (P. Canestrari, E. Emer, A. Gualandi, and P.G. Cozzi, unpubUshed results). The procedure was recently extended to the formation of quaternary stereogenic centers, in particular the alkylation of a-branched aldehydes with the benzodithiolyUum ion can be catalyzed by the use of 9-amino-9-deoxy-epi-dnchona alkaloid primary amines [35]. The use of primary... 

No evidence could be obtained for the formation of 2ff-benzo[i>]thiet or its valence tautomer by irradiation of 3/f-l, 2-benzodithiole l,l-dioxide. Naphtho-[l,8-6c]thiet (58) has been prepared and its 5-oxide, and S -dioxide, have been obtained by oxidation with m-chloroperoxybenzoic acid. All three compounds react with lithium aluminium hydride to give ring-opened products as the result of hydride attack on sulphur. After reduction and methylation, (58) gave the methyl sulphide (59), and the 5-oxide gave bis(a-naphthyl) disulphide (75%) together with (58) (6%) and the corresponding sulphone (4%), which was the major product (85%) from the 55-dioxide (Scheme 8). Thiets are believed to be... 

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