Dual reactivity of B(C6F5)3 enables the silylative cascade conversion of: N -aryl piperidines to sila-N-heterocycles: DFT calculations

TY - JOUR

T1 - Dual reactivity of B(C6F5)3 enables the silylative cascade conversion of

T2 - N -aryl piperidines to sila-N-heterocycles: DFT calculations

AU - Zhou, Miaomia

AU - Park, Sehoon

AU - Dang, Li

N1 - Publisher Copyright: © the Partner Organisations 2020.

PY - 2020/4/7

Y1 - 2020/4/7

N2 - The first catalytic access to bridged sila-N-heterocycles from piperidines via cascade sp3 and sp2 C-Si bond formation all mediated by a single catalyst B(C6F5)3 (A) has been recently developed by Park and Chang. Described herein is a theoretical study of the B(C6F5)3-catalyzed silylative cascade conversion of N-aryl piperidines (H) to afford polycyclic azasilaheterocycles with a strong emphasis on the dual reactivity of B(C6F5)3. The DFT calculations show that the catalyzed reaction involves three steps of the cascade reaction: (i) the formation of tetrahydropyridine (I) upon dehydrogenation of the piperidine; (ii) β-selective hydrosilylation of tetrahydropyridine; (iii) an intramolecular sila-Friedel-Crafts reaction to form a bridged sp2 C-Si bond. The N-silyl piperidinium borohydride (A′) turns out to be the thermodynamically favored, resting species of the overall reaction, which is consistent with the observation of a species such as A′ during borane catalysis. The DFT calculations suggest that the β-selective hydrosilylation of I is the rate-determining step in the entire catalytic cycle, while the liberated I reacts with B(C6F5)3 to form a zwitterion consisting of iminium and borate units (O). The calculated sila-Friedel-Crafts reactions of a range of presupposed silylated (cyclic)aza intermediates imply the importance of structural integrity on the piperidinyl unit of substrates.

AB - The first catalytic access to bridged sila-N-heterocycles from piperidines via cascade sp3 and sp2 C-Si bond formation all mediated by a single catalyst B(C6F5)3 (A) has been recently developed by Park and Chang. Described herein is a theoretical study of the B(C6F5)3-catalyzed silylative cascade conversion of N-aryl piperidines (H) to afford polycyclic azasilaheterocycles with a strong emphasis on the dual reactivity of B(C6F5)3. The DFT calculations show that the catalyzed reaction involves three steps of the cascade reaction: (i) the formation of tetrahydropyridine (I) upon dehydrogenation of the piperidine; (ii) β-selective hydrosilylation of tetrahydropyridine; (iii) an intramolecular sila-Friedel-Crafts reaction to form a bridged sp2 C-Si bond. The N-silyl piperidinium borohydride (A′) turns out to be the thermodynamically favored, resting species of the overall reaction, which is consistent with the observation of a species such as A′ during borane catalysis. The DFT calculations suggest that the β-selective hydrosilylation of I is the rate-determining step in the entire catalytic cycle, while the liberated I reacts with B(C6F5)3 to form a zwitterion consisting of iminium and borate units (O). The calculated sila-Friedel-Crafts reactions of a range of presupposed silylated (cyclic)aza intermediates imply the importance of structural integrity on the piperidinyl unit of substrates.

UR - http://www.scopus.com/inward/record.url?scp=85082769054&partnerID=8YFLogxK

U2 - 10.1039/c9qo01437c

DO - 10.1039/c9qo01437c

M3 - 文章

AN - SCOPUS:85082769054

SN - 2052-4110

VL - 7

SP - 944

EP - 952

JO - Organic Chemistry Frontiers

JF - Organic Chemistry Frontiers

IS - 7

ER -