Bi-spirooxindoles

The Michael addition/cyclization of isothiocyanato oxindoles (296), catalysed by the quinine-derived thiourea (288b) and its analogues, has been employed for the preparation of a variety of 3,2 -pyrrolidinyl spirooxindoles (297) and bis-spirooxindoles (298) with <98% ee and >20 1 dr (Scheme 15). " ... 

SCHEME 5.7. Microwave-assisted diastereoselective synthesis of an original bis-spirooxindoles via a hydrazone formation/Wolff rearrangement/1,2-hydrogen shift/l,3-dipolar cycloaddition consecutive sequence. 

In a separate investigation by Porco, Jr. and coworkers, the isatin derivative 134 (R = H) was converted to spirooxindole pyran 141 in 13 1 dr and 99% ee by means of a Prins-type cyclization involving homoaUyhc alcohol 140 [79]. The diastereos-electivity of the transformation has been proposed to arise from a preferred chairlike transition state with the benzenoid ring of oxindole in a pseudoequatorial orientation. Spirooxindole oxepenes also were prepared via diastereoselective spiro-annulation of isatins with bis-homoallyhc alcohols. 

Keywords Isatin, hydrazine hydrate, l,l-bis(methylthio)-2-nitroethylene, ethanol, room temperature, one-pot multicomponent reaction, spirooxindole-pyrazolines... 

To a solution of l,l-bis(thiomethyl)-2-nitroethylene (2 1 mmol) in ethanol (4 mL) in a 10 mL flask was added NH2NH2 H2O (3 80% aq., 2 mmol) and stirred for 5 h at room temperature. After then, isatin (1 2 mmol) was added to the reaction mixture, and stirring was continued for another 3-7 h. On completion of the reaction, the crude precipitated was filtered and washed with cold ethanol to obtain piu-e product of spirooxindole-pyrazoline 4. All the products were characterized by spectral studies. 

Hydrogen-bonding catalysis of the Diels-Alder reaction of 2-vinylindoles 39 and methylene-indolinones 69 has been accomplished by the Barbas group using a C2-symmetric bis-thiourea organocatalyst [31]. This efficient transformation provided a powerful approach by which to construct carbazole-spirooxindole derivatives 71 extremely rapidly (less than 10 min) with excellent enantiopurity and structure diversity (Scheme 38.20). 

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