Catalyst-Controlled Product Selectivity for Cycloaddition of Bis(indol-3-yl)-allenes to Fused Spiroindolines and
Yan-Yan Zhang1, Yin Wei1, Min Shi1,2
1State Key Laboratory of Organometallic Chemistry, Center for Excellence in Molecular Synthesis , Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences , 345 Lingling Road , Shanghai 200032 , People's Republic of China.
Abstract:
A catalyst-controlled cycloaddition reaction of bis(indol-3-yl)-allenes gives rise to two different types of fused spiroindolines bearing a spiro quaternary stereocenter, affording a range of fused spiroindolines in good yields. The asymmetric desymmetrization of bis(indol-3-yl)-allenes with very high regioselectivities and excellent enantioselectivities has been successfully established and catalyzed by (R)-DTBM-Segphos(AuNTf2)2. Mechanistic studies through control experiments and DFT calculations provide plausible mechanistic proposals.
Related Concept Videos
Cycloaddition Reactions: Overview
Diels–Alder Reaction Forming Bridged Bicyclic Products: Stereochemistry
Cycloaddition Reactions: MO Requirements for Thermal Activation
[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction
Diels–Alder Reaction Forming Cyclic Products: Stereochemistry
Regioselectivity and Stereochemistry of Hydroboration
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn stereochemistry.


![Solid-phase Synthesis of [4.4] Spirocyclic Oximes](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F58508.jpg&w=3840&q=50)