Preparation and cycloaddition reactions of silylated thiophene 1,1-dioxides

Toward poly(aminophthalimide), structures of dimers and trimers

“…37 2,5-Diiodothiophene-1,1-dioxide (15) was selected as a diene substrate because elimination of sulfur dioxide from the Diels-Alder adduct and the subsequent aerobic oxidation to aromatize the product were highly expected to take place spontaneously after the [4+2] cycloaddition. 38 Indeed, heating a mixture of 15 and 13b or 13c in DMF at 130 C for 18-22 h gave the corresponding 3,6-diiodophthalimides 17b,c, albeit in rather low yields. 3,6-Dibromo-N-trialkoxyphenylphthalimide 16c could be also prepared by this method.…”

The synthesis and transformations of fused bicyclo[2.2.2]octenes

“…There are various ways of preparing bicyclo[2.2.2]oct-7-ene-tetracarboxylic acid dianhydride derivatives 6; one of the most usual being a double Diels−Alder cycloaddition of maleic anhydride (8), acting as a dienophile onto the 2H-pyran-2-one core 7 (Scheme 2). 4 The first intermediate in the synthesis is a bicyclic bridged lactone 9, which is formed through the usual thermal [4+2] cycloaddition reaction.…”

“…), 6 a spontaneous extrusion of CO 2 immediately follows the cycloaddition step and another diene 10 is formed. The latter reacts with a second molecule of maleic anhydride (8), thus forming a double cycloadduct 6.…”

“…It again reacts with another molecule of dienophile, yielding the product with a bicyclo[2.2.2]octene skeleton. 8 It is also worth mentioning that the starting diene does not need to be a cyclic compound. For example, the reaction of (1E,3E)-4-(trimethylsilyl)buta-1,3-dienyl acetate with maleic anhydride produced 6a (6: R 1 =R 2 =R 3 =R 4 =H) in a 95% yield after one hour of heating at 100 °C, and in the absence of a solvent.…”

“…10 We reported the synthesis of a series of highly substituted double cycloadducts, bearing a protected amino substituent at the bridgehead carbon atom. These were obtained with the cycloaddition of maleic anhydride (8) (Scheme 4). 13 With the use of refluxing tetralin we were able to synthesize the doublecycloaddition products 15a-k in short reaction times with good-to-excellent yields ( Table 1).…”