3- allyl-3-aryl oxindoles

Trost and his co-workers succeeded in the allylic alkylation of prochiral carbon-centered nucleophiles in the presence of Trost s ligand 118 and obtained the corresponding allylated compounds with an excellent enantioselec-tivity. A variety of prochiral carbon-centered nucleophiles such as / -keto esters, a-substituted ketones, and 3-aryl oxindoles are available for this asymmetric reaction (Scheme jg) Il3,ll3a-ll3g Q jjg recently, highly enantioselective allylation of acyclic ketones such as acetophenone derivatives has been reported by Hou and his co-workers, Trost and and Stoltz and Behenna - (Scheme 18-1). On the other hand, Ito and Kuwano... 

Condensation of resin bound ketones with hydrazines followed by cyclizative cleavage was used in a synthesis of pyrazolinones [67]. Samarium iodide induced radical cyclization of allyl aryl ethers led to benzofuran derivatives [68]. Kurth et al. have reported a two reaction iterative process for the construction of polyisoxazolines [69] and polyisoxazoles [70]. An intramolecular Heck reaction has been employed to prepare 2-oxindole derivatives [71]. 

In 2010, Dorta and coworkers [83] reported a new synthetic strategy to access functionalizable 3-allyl oxindoles bearing a chiral quaternary carbon stereocenter via a direct palladium-catalyzed a-arylation protocol. This elegant methodology, previously accessible only via a two-step procedure involving a Pd-catalyzed intramolecular a-arylation followed by an asymmetric Pd-catalyzed allylic alkylation [84], afforded impressive reactivities, and high chemoselectivities and enantioselectivities were also achieved in the synthesis of oxindoles using a new chiral Pd-NHC catalyst (Scheme 8.45). 

An interesting palladium-catalyzed cascade reaction leading to 3,3-disubstituted oxindoles 190 starting from 2-(alkynyl)aryl isocyanates 189 with benzylic alcohols has been developed by Toyoshima et al. [76] (Scheme 6.53). This reaction integrates a cyclization step and a novel [1,3] rearrangement step. Both benzylic and allylic alcohols could be introduced efficiently to this domino process. Furthermore, the products of this reaction are an important class of heterocycles which are often found in naturally occurring and biologically active molecules. 

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