Synthesis of hindered spiro-oxindoles by photolysis of 1-(1-alkenyl)benzotriazoles

Recent developments in indole ring synthesis—methodology and applications

“…The photolysis of o-alkynyltelluroimidates yields 3-acylindoles, 457 and the photolysis of the benzotriazolyladamantane 56 leads to oxindole 57 after hydrolysis (Scheme 111). 458, 459 This reaction, which was first discovered by Wender and Cooper, 460 has been employed in a total synthesis of gelsemine. 461 Photolysis of α-diazo ketone 58 affords indolylketene 59 which is only stable below 58 K. Above this temperature tetrameric indole 60 forms in high yield (Scheme 112).…”

Benzotriazole-Mediated Synthesis of Oxygen-Containing Heterocycles

“…For instance, the photolysis of 1-(benzotriazole-1-yl)-methoxymethylene adamantane 51a afforded a 1:1 separable mixture of 2-iminooxetane 52a and 53a in a combined yield of 80%, demonstrating the ability of this reaction to form a C-C bond within a sterically congested environment. Even more steric congestion had no perceptible effect on the reaction outcome in case of substrate 51b: irradiation of 51b by high pressure mercury lamp yielded a separable 1:1 mixture of photoadducts 52b and 53b in a combined yield of 70% (Scheme 12) [29,30]. …”

Synthesis of Heterocycles Mediated by Benzotriazole. 2. Bicyclic Systems

“…45 Photolysis of adamantanylidene derivatives 160 gives spiro-3H-indoles 161 in 31À44% yields (Scheme 36). 46 These examples indicate that the photochemical conversion of benzotriazole to indole derivatives is quite insensitive to steric hindrance at the reacting centers.…”