The domino carbocyclization of alkenylboronic acids with γ- or δ- cyano-N-tosylhydrazones developed recently in our research group leads to cyclic ketones involving the formation of two C(sp3)- C(sp2) bonds on the same C atom with complete diastereoselectivity. An stereoselective reductive alkenylation of the tosylhydrazone with the boronic acid, followed by cyclization of the intermediate allylboronic acid explains the formation of the final products A. We envisioned that starting from N-tosylhydrazones featuring the tethered electrophilic group in an aromatic ring, more sophisticated polycyclic structures B like 2,2-disubstituted-a-tetralones and indanones could be synthesized. Gratifyingly, the expected carbocycles were obtained in one synthetic step. A domino sequence involving diazo compound formation/reductive alkenylation/1,3-borotropic rearrangement/ intramolecular bora-aza-ene reaction is proposed. Mechanistic DFT calculations have been made to support the fact of the one side approximation of the allylboronic acid intermediate to lead to these stereocontroled structures. Our most recent advances in the field are focused on the employment of other tethered electrophilic substituents, which gain access to novel structures featuring a quaternary sterocenter. Moreover, the employment of more activated boron derivatives is also currently pursued.

Domino stereoselective synthesis of β,γ-unsaturated ketones from alkenylboronic acids and tosylhydrazone-tethered nitriles

2019 Fall National Meeting

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