Action of Grignard reagents on thiophthalic anhydride, 3‐benzal‐2‐thiophthalide, 3‐p‐chloro‐ and 3‐p‐methoxybenzalphthalides

Abstract

Thiophthalic anhydride 1 reacts with the GRIGNARD reagents 2a–e (1:1 mol.) to give the corresponding 3‐aryl(alkyl)‐3‐hydroxy‐2‐thiophthalides 3a–e. The interaction of 1 with 2c and f (1:2 mol.) yields the corresponding 1,2‐diaroylbenzene derivatives 4. On the other hand, 1 reacts with 2b (1:2 and 1:3 mol.) to give 5 and 6, respectively. When 3‐benzal‐2‐thiophthalide 7a and 3‐p‐chlorobenzalphthalide 7b are allowed to react with the GRIGNARD reagents 2c–f, the corresponding indenone derivatives 8 are obtained. On the other hand, the reaction of 7a and b with 2b (1:2 mol.) yields 6 and 9, respectively. 7a and p‐methoxybenzalphthalide 7c react with 2b (1:1 mol.) to give 5 and 10 (a and b). The constitution of the products has been investigated by means of IR and UV spectra.

Temperature Dependence of the Reduction of Phthalic Thioanhydrides by NaBH4: Competition between 3-Hydroxythiolactone and Phthalide Formation

“…Paulussen et al8 described the synthesis of 3‐benzyl‐3‐hydroxy‐2‐thiophthalide in 1996 from the reaction of 1a with benzylmagnesium chloride using a literature procedure 9. The initially obtained disubstituted thiolactone was dehydrated to the benzylidene‐2‐thiophthalide, which was envisaged as a potential chain‐stopper in the polymerisation reaction leading to poly(isothianaphthene) (PITN).…”

Grignard Reactions on Ortho Dicarboxylic Arene Derivatives. Synthesis of 1,3-Dithienylisothianaphthene Compounds

“…In a Grignard reaction with 2-thienylmagnesium bromide as the Grignard reagent one can use different substrates. In literature the use of 5a , , phthalic anhydride , and thiophthalic anhydride , has been reported in the synthesis of ortho diketones. However, the results of different authors appeared not to be entirely consistent with one another.…”