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This account describes the use of phosphines as simple organocatalysts that catalyze the synthesis of complex spirocyclic compounds. Besides our own results, coverage of relevant literature in this field is also provided, including asymmetric variants and synthetic applications. 1 Introduction 2 Cycloaddition Reactions Involving Allenoates or 2-Butynoates 2.1 [3+2] Cycloadditions 2.2 [4+2] Cycloadditions 2.3 [4+1] Cycloadditions 3 [3+2] Cycloadditions with Morita–Baylis–Hillman Adducts 4 Cycloaddition Reactions Using Ynone Derivatives 5 Cycloaddition Reactions Involving Methyl Vinyl Ketone ­ Derivatives 6 Miscellaneous Reactions 7 Conclusions

Triphenylphosphine promoted reactions between 3-arylideneoxindoles and δ-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 δ-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.

The phosphine-promoted [3 + 2] cyclizations between γ-substituted allenoates and arylideneoxindoles have been applied to the stereoselective synthesis of spiro(cyclopentene)oxindoles with trisubstituted cyclopentene units. It has been demonstrated that PPh(3) 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.