Phthalic thioanhydride

Phthalic hydrazide tautomerism, 3, 4 Phthalic thioanhydride reactions, 4, 824-825... 

Phthalic thioanhydride is the benzologue of maleic thioanhydride. Its behaviour with various reducing agents is shown in Scheme 159 <72AHC(14)33l). Reaction with three equivalents of phenylmagnesium bromide followed by oxidative hydrolysis gives o-diben-zoylbenzene with only one equivalent of PhMgBr, o-benzoylbenzoic acid is formed (50%). 

Alkylidene derivatives of phthalic thioanhydride are formed as shown in Scheme 160. Reaction of phthalic thioanhydride with hot triethyl phosphite produces trafts-S -bithioph-thalide (457), probably via the carbene and phosphorane (Scheme 161) (72AHC(14)331>. Support for this mechanism stems from the fact that brief treatment of phthalic thioanhydride with triethyl phosphite in the presence of phthalic anhydride gives (458) in the presence of benzaldehyde the same reaction leads to the benzylidene derivative (456). An alternative mechanism has also been suggested, in which the penultimate step is the formation of an epoxide, which is deoxygenated to yield the product (72AHC(14)331>. 

The parent compound (5) may be prepared by heating o-xylylene dibromide (a,a -dibromo-o-xylene) with sodium or potassium sulfide, usually in aqueous ethanol (see Table I for references), or by reducing phthalic thioanhydride (Section VII, B) with aluminum hydride or diborane 20 the former procedure has been used to prepare a number of derivatives of 5 (Table I). Disodium o-xylylenedimercaptide (6) can be isolated from the reaction between o-xylylene dibromide and... 

An attempt to scale up the synthesis of 2-thiophthalide by the reduction of phthalic anhydride with hydrogen sulfide gave 3,3 -bithiophthalide (106a), which arises by condensation of 2-thiophthalide (98) with phthalic thioanhydride (104) (Scheme III).118... 

At one time phthalic thioanhydride was thought to have the structure 120a and derivatives (e.g., 120b) were thought to have similar structures. X-Ray crystallographic data for 4,5-dimethyl-... 

Phthalic thioanhydride forms charge-transfer complexes with A.A-diethylaniline and various aromatic hydrocarbons (e.g., a 1 1 complex with naphthalene).131 When oxygen and sulfur are members... 

The polarographic reduction of phthalic thioanhydride has been studied.183,134... 

Phthalic thioanhydride is reduced by aluminum hydride or diborane to l,3-dihydrobenzo[c]thiophene (100%) (Section III,A),20 by one equivalent of lithium aluminum hydride to o-phthalaldehyde... 

Phthalic thioanhydride (104) reacts some thousand times faster with hot triethyl phosphite (TEP) to give 3,3 bithiophthalide... 

Phthalic thioanhydride (104) does not react with triphenyl-phosphine, but it reacts with tris(dimethylamino)phosphine to give a... 

A number of other reactions of phthalic thioanhydride have been described by Reissert and Holle.125... 

Dihydrobenzo[c]thiophene (Section III,A) is also known as 1,3-dihydroisothianaphthene, 2-thiaindane, o-xylylene sulfide (commonly used), thiophthalan, 3,4-benzothiacyclopentane, and 3,4-benzo-2,5-dihydrothiophene. In this case we have used the first-mentioned name throughout other problems of nomenclature are discussed as they arise. Since I,3-dihydrobenzo[c]thiophenes are important intermediates in this field, their chemistry is discussed in detail. With other derivatives such as 2-thiophthalide (Section VII, A) and phthalic thioanhydride (Section VII, B), which may be regarded as l,3-dihydrobenzo[c]thiophen-l-one and 1,3-dihydro-benzo[c]thiophen-l,3-dione, respectively, our coverage of the literature may be incomplete, since we have only included references which arose directly or indirectly (i.e., as cross references) by searching benzo[c]thiophene or equivalent terms in CA. 

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