Anion capture alkene carbopalladation

Various examples of intramolecular stereoselective carboamination have been reported28 "30. Asymmetric synthesis of key intermediates for capnellenols is achieved via a Heck-type intramolecular carbopalladation of an alkene with a vinyl halide and amide anion capture in the presence of Chiraphos- or BINAP-modified palladium catalysts31. 

Carbopalladation reactions yield another carbon-bound palladium complex 13, which can undergo a variety of reactions (Scheme 2). The most common pathway yields an alkene 14 via a 5yn-/S-hydride elimination. Two other useful reactions are carbonylation (13- 15) and anion capture (13- 16), which provide opportunities for further function-alization.t Additionally, carbopalladation products can be induced to undergo another carbopalladation reaction, creating the opportunity to forge multiple carbon-carbon bonds. Simple combinations of palladium complex precursors and reactions quickly... 

Several other types of domino reactions have been employed in the synthesis of natural products. Diastereoselective conversion of allylic carbonate 173 into enone 174 was one key transformation in a total synthesis of (+)-3-isorauniticine 175 (Scheme 27).Treatment of allylic sulfonamide 173 with a palladium catalyst re-gioselectively forms a 7r-allylpalladium intermediate by carbonate displacement. Carbopalladation of the pendant alkene, carbonylation, a second intramolecular alkene insertion, and /3-hydride elimination delivers a 67 22 11 mixture of stereoisomers of which enone 174 is the major product (isolated in 45-53% yield). Carbopalladation products can also undergo anion capture reactions. For instance, during the synthesis... 

Ma has developed a three-component allene carboamination reaction for the stereoselective synthesis of 2,5-as-disubstituted pyrrolidine derivatives [54]. A representative transformation involving allene 58, 4-iodoanisole, and imine 59 that generates 60 in 90% yield is shown below (Eq. (1.28)). The reaction is believed to proceed through the intermediate Jt-allylpalladium complex 62, which is formed by carbopalladation of the alkene to give 61 followed by addition of the malonate anion to the activated imine. Intramolecular capture of the allylpalladium moiety by the pendant nitrogen nucleophile affords the pyrrolidine product. A related asymmetric synthesis of pyrazolidines that employs azodicarboxylates as one of the electrophilic components has also been reported [55]. The pyrazolidine products are obtained with up to 84% ee when chiral bis oxazolines are employed as ligands. 

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