The Role of Fluorine Substituents in the Regioselectivity of Intramolecular C-H Bond Functionalization of Benzylamines at Palladium(II)

TY - JOUR

T1 - The Role of Fluorine Substituents in the Regioselectivity of Intramolecular C-H Bond Functionalization of Benzylamines at Palladium(II)

AU - Milani, Jessica

AU - Pridmore, Natalie E.

AU - Whitwood, Adrian C.

AU - Fairlamb, Ian J S

AU - Perutz, Robin N.

PY - 2015/9/14

Y1 - 2015/9/14

N2 - The effect of fluorine substituents on the regioselectivity of intramolecular reactions of mono- and difluorinated N,N-dimethylbenzylamines (1a-f) at palladium, to form palladacycles di-μ-acetatobis[o-dimethylaminomethyl-n-fluorophenyl-C,N)dipalladium(II) (2a-f) and di-μ-chlorobis[o-dimethylaminomethyl-n-fluorophenyl-C,N)dipalladium(II) (3a-e), has been investigated. When fluorinated substrates with two sites available for the C-H functionalization (1c and 1e) undergo cyclopalladation via a CMD mechanism (acetate-bridged palladacycles), they do not exhibit regioselectivity. In contrast, the same substrates exhibit complete regioselectivity for the C-H functionalization para to fluorine in cyclopalladation reactions that proceed via an SEAr mechanism (involving chloride-bridged palladacycles). X-ray crystal structures were obtained for all the palladacycles synthesized, and a structural analysis showed that the number and the position of the fluorine atoms on the aromatic ring have a marked effect on the "clamshell" structure of the acetate-bridged palladacycles. By contrast, there is no great variation in the structures of the planar chloride-bridged palladacycles.

AB - The effect of fluorine substituents on the regioselectivity of intramolecular reactions of mono- and difluorinated N,N-dimethylbenzylamines (1a-f) at palladium, to form palladacycles di-μ-acetatobis[o-dimethylaminomethyl-n-fluorophenyl-C,N)dipalladium(II) (2a-f) and di-μ-chlorobis[o-dimethylaminomethyl-n-fluorophenyl-C,N)dipalladium(II) (3a-e), has been investigated. When fluorinated substrates with two sites available for the C-H functionalization (1c and 1e) undergo cyclopalladation via a CMD mechanism (acetate-bridged palladacycles), they do not exhibit regioselectivity. In contrast, the same substrates exhibit complete regioselectivity for the C-H functionalization para to fluorine in cyclopalladation reactions that proceed via an SEAr mechanism (involving chloride-bridged palladacycles). X-ray crystal structures were obtained for all the palladacycles synthesized, and a structural analysis showed that the number and the position of the fluorine atoms on the aromatic ring have a marked effect on the "clamshell" structure of the acetate-bridged palladacycles. By contrast, there is no great variation in the structures of the planar chloride-bridged palladacycles.

UR - http://www.scopus.com/inward/record.url?scp=84941584531&partnerID=8YFLogxK

U2 - 10.1021/acs.organomet.5b00608

DO - 10.1021/acs.organomet.5b00608

M3 - Article

AN - SCOPUS:84941584531

SN - 0276-7333

VL - 34

SP - 4376

EP - 4386

JO - Organometallics

JF - Organometallics

IS - 17

ER -