✍ Scribed by Takehiko Nishio; Mitsuru Oka
No coin nor oath required. For personal study only.
The photochemical synthesis of indole derivatives starting from the indoline-2-thiones 1 is described. Irradiation of indoline-2-thiones 1 in the presence of alkenes 3 gave 2-alkyl-3H-indoles 4-7 or 2-alkylindoles 8-22 through the ring cleavage of the intermediates, spirocyclic amino-thietanes, initially derived by [2 + 21 cycloaddition of the C=S bond of 1 and the C=C bond of 3. Irradiation of 1 in the presence of trialkylamines 26 gave desulfurization products 27-32 and unexpected 3-alkylindoles 33-40. N-Acylindoline-2-thiones 1 I-p yielded the deacylated products, indoline-2-thiones 1 a-b, and ethyl esters 43 through y-H abstraction by the excited thioamide S-atom when irradiated in CDCIJEtOH or benzene/EtOH. Oxygen analogues 2a-d also underwent intramolecular H abstraction to give the indolin-2-ones 2e-f and ethyl esters 43 in a similar way.
-In recent years, there has been great interest in the photochemistry of thioamide compounds from both synthetic and mechanistic view points [l]. In particular, they undergo [2 + 21 photocycloadditions with alkenes to yield amino-thietanes as primary products, which are usually unstable and are transformed into fragmentation products (Schemr I). This may be ascribed to the participation of the lone-pair electrons on the N-atom, which facilitate the C-S bond cleavage of the thietane ring leading to zwitterions, and then they undergo further reactions [l c-d]. In the course of our studies of the photochemical reactions of cyclic conjugated nitrogen-thiocarbonyl systems [2], we found that photochemically induced addition of thioamides to alkenes provided a convenient method for the C-C bond formation of N-containing heterocycles [2a-d, g, j-k, m]. We recently reported that photodesulfurization reactions of indoline-2-thiones and 3,3-disubstituted indoline-2-thiones to indoles [2 el and indolines [2 fl, respectively, and [2 + 21 photocycloaddition reaction of 3,3-disubstituted indoline-2-thiones with electron-poor alkenes leading to 2-alkylideneindolines [2 g]. Das and coworkers have shown that indoline-2-thiones undergo photoinduced addition to electron-poor alkene, methyl methacrylate, to give a mixture of isomeric 2-substituted indoles [3]. To see the scope and limitation of the photoaddition of indoline-2-thiones 1 and alkenes, we examined the photoreactions of 1 with a variety of alkenes 3 including electron-rich ones and related photoreactions of 1 (Table i). Scheme I -Further products hv < + ; ; c + ;a:: RZN-bN k -Alkene: R2!9 ___) CR'2=CR'2 R' Amino-thietane
📜 SIMILAR VOLUMES
1 9. VI. 90
## Abstract Indoline‐2‐thiones **1a‐b,d,f,h**, which have at least one hydrogen at the 3‐position reacted with α‐halo ester **2a‐d**, α‐halo ketones **2e‐f**, and a‐bromoacetonitrile **2g** to give 2‐alkylthioindole derivatives **3–11**. In a similar manner treatment of 3,3‐disubstituted indoline‐2
## Abstract The antioxidant behavior of a series of new synthesized substituted indoline‐2‐ones and indolin‐2‐thiones was investigated in this study using an oxygen radical absorbance capacity assay (ORAC$\_{ROO\mathop{\bullet}^{\!\!\!\!-}}$) and 2,2′‐azobis(2‐amidino‐propane) dihydrochloride (AAPH
## Abstract The photocycloaddition of benzothiazole‐2‐thiones to electron‐rich and aryl‐substituted alkenes are described. Irradiation of __N__‐unsubstituted benzothiazole‐2‐thione (1) in the presence of alkenes 3 gave 2‐(2′‐mercaptoalkyl)benzothiazoles 4, and 2‐substituted benzothiazoles 5 and 6 (