Rhodium-Catalyzed Diastereoselective [4+2] Cycloisomerization of Allenyldienes

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2020-12

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Abstract

The diastereoselective [4+2] cycloisomerization of allenyldienes is established. Using the method reported by Ma chiral dienylallenes are synthesized. The ability of these molecules to then undergo the rhodium catalyzed [4+2] cycloisomerization analogous to thermal Diels-Alder reaction is reported. 29 examples with tethers possessing nitrogen, oxygen and carbon are presented. Selectivities range from >99:1 to 90:10 in most examples. A new cationic rhodium complex [Rh(cod)dppeO]SbF6 complex has been synthesized and the structure was illustrated with X-ray single crystal. The reaction can be run under different conditions. Either 5 mol% of the catalyst, [Rh(cod)dppeO]SbF6 complex, can be used in the reaction or 2.5 mol% [Rh(cod)Cl]2 can be mixed with 5 mol% dppe(O) to form the catalyst in situ; both approaches provide essentially the same result.

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rhodium catalyst, diastereoselective cycloisomerization

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