Rhodium-Catalyzed Stereoselective Cyclization of 3-Allenylindoles and N-Allenyltryptamines to Functionalized Vinylic Spiroindolenines

Abstract

Herein, we report a highly enantio- and diastereoselective rhodium-catalyzed cyclization of N-allenyltryptamines and 3-allenylindoles to 6-membered spirocyclic indolenines. This allylic addition methodology offers the advantage of using a comparably cheap commercially available ligand with low loadings of an affordable rhodium precursor. The products can be converted into functionalized spirooxindoles and spiroindolines, which are regarded as important building blocks for the synthesis of a lot of natural products with biological activities.

Intramolecular Buchwald-Hartwig N-Arylation of Bicyclic Hydrazines: Practical Access to Spiro[indoline-2,3'-piperidines]

“…To the best of our knowledge, the preparation of such original spiro scaffolds has not been reported in the literature to date, although spiro[indoline-3,4'piperidine] or spiro[indoline-3,3'-piperidine] derivatives are known. [40][41][42][43] Herein, a versatile procedure to generate a new class of spiro compounds is described. This strategy involves an unprecedented intramolecular Buchwald-Hartwig N-arylation of bicyclic hydrazines as a key synthetic step.…”

Copper-catalyzed oxidative dehydrogenative dearomatization of indole derivatives: A new strategy to construct spirocyclic indolenines

“… 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 Moreover, spiroindolenines have emerged as a promising scaffold for furnishing various synthetic transformations. 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 The unique rigid structure of spiroindolenines makes them suitable candidates in organic optoelectronics. Consequently, numerous approaches have been developed to access functionalized spiroindolenines in synthetic chemistry and material science.…”

Enantioselective and Diastereodivergent Synthesis of Spiroindolenines via Chiral Phosphoric Acid-Catalyzed Cycloaddition

“…A number of enantioselective methodologies have been successively reported over the years . However, in contrast to spirocyclohexyl-oxindoles, asymmetric strategies for building related indolines and indolenines are limited in number . Pd-catalyzed spiroindolenine synthesis was reported in 2014 by You et al and illustrated in a single enantioselective example leading to modest enantioenrichment (52% ee) .…”