Synthesis of 3,3′-Spirocyclic Oxindoles via Phosphine Catalyzed [4 + 2] Cyclizations
摘要:
Triphenylphosphine promoted reactions between 3-arylideneoxindoles and (delta-aryl-substituted penta-2,3-dienoates afford an unprecedented access to spirocyclic oxindoles with functionalized six-membered rings. In these new [4 + 2] cyclization processes, the allenoates operate as the four-carbon synthons, thanks to the involvement of the substituted (delta-carbons. These reactions give excellent control of the relative stereochemistry of the three stereogenic centers. The stereochemistry of the final product has been ascertained by X-ray diffraction studies.
Power of P: Phosphine‐promoted [3+2] annulation reactions between electron‐poor allenes and 3‐arylidene indolin‐2‐ones afford a new organocatalytic strategy for the synthesis of the spirocyclic core of oxindolic cyclopentanes (see scheme). Asymmetric variants of these reactions have been implemented by using chiral catalysts, giving very high levels of asymmetric induction.
The phosphine-promoted [3 + 2] cyclizations between gamma-substituted allenoates and arylideneoxindoles have been applied to the stereoselective synthesis of spiro(cyclopentene)oxindoles with trisubstituted cyclopentene units. It has been demonstrated that PPh3 operates a very efficient control of the relative stereochemistry of the three stereogenic centers of the final spiranic products. Focused experiments have been carried out then so as to access carbocyclic analogues of an important series of anticancer agents inhibiting MDM2-p53 interactions.