Carbohydrate-Derived Ligands in Asymmetric Tsuji–Trost Reactions - Carbohydrates: Tools for Stereoselective Synthesis - page 213

R

R R

R

S S

LG LG

Pd

Pd

L'

L

L L'

Coordination

R

R Oxidative

addition LG

Dissociation

Nu

R R

R

Nu R

R R

Nu

Pd Pd Pd

Nucleophilic
addition

L L' L L'

L L'

W-type M-type

L,L'=mono- or bidentate ligand; S=solvent or vacant; LG=leaving group; Nu=Nucleophile

Scheme 10.1

Accepted mechanism for Pd-catalyzed allylic substitutions.

Type A

R

R

PdL* n R

R R

Nu -

R

*

X
S1 R= Ph; X= OAc
S2 R= i Pr; X= OCO 2 Et
S3 R= Me; X= OAc

Nu

PdL* m

X Nu

PdL* n

Nu -

*

n n n

PdL* m

S4 n=1; X= OAc
S5 n=2; X= OAc

Type B

H

R

PdL* n

H X

S6 R= Ph; X= OAc
S7 R= 2-Napthyl; X= OAc

H

R

H

Nu -

R

*

H

H

Nu

PdL* m

or

X R PdL* n

H H

S8 R= Ph; X= OAc
S9 R= 2-Napthyl; X= OAc

Scheme 10.2

Two classes of asymmetric allylic substitution reactions.