Topics in Current Chemistry (2020) 378:16
1 3
elaboration of vinylbenzyldimethylsilane-containing products via Hiyama crosscoupling. In addition, this protocol enabled efficient synthesis of a key intermediate
en route to the selective serotonin reuptake inhibitor sertraline.
Gong et  al. have disclosed a synergistic palladium/tertiary amine Lewis base
catalysis to prepare enantioenriched dihydropyridones and β-lactams (Scheme  25)
[34]. Using a Pd-catalyzed carbonylation process in combination with a newly
developed isothiourea catalyst (fused-BTM), 22 dihydropyridones and 6 β-lactams
were prepared in good yields and control over diastereo- and enantioselectivity. The
N-tosyl group could be reductively cleaved and the product elaborated.
The mechanism proposed involves Pd-catalyzed carbonylation of the benzyl bromide before conversion of the resulting acylpalladium species to an arylketene via
β-hydride elimination (Scheme  26). Interception of this ketene with fused BTM
[Pd 0 ]
[Pd II ]
Br
[Pd II ] Br
O
[Pd II ]
H
Br
Ar
O
Ar
Ar
NR 3
NR 3
O
Ar
R 1
NTs
R 2
NR 3
O
Ar
R 1
R 2
NTs
NTs
O
Ar
R 1
R 2
Palladium-Catalyzed
Carbonylation/β-Hydride
Elimination
1,4-Addition/
Cyclisation
Proposed Mechanism:
Scheme 26 Proposed mechanism for the carbonylation/cyclization cascade
O
OPfp
O
OPfp
O
R 2
OCO 2
t Bu
(R)- or (S)-[Ir] (2 mol%)
(R)-BTM (10 mol%)
THF, rt
17 Examples
R 2
R 1
O P
N
Ph Ph
Ir
Ph
(R)-[Ir]:
OPfp
O
OPfp
O
OPfp
O
S
F 3 C
MeO
N
N
Me
90%
11:1 d.r., 98% ee
98%
17:1 d.r., >99% ee
74%
>20:1 d.r., >99% ee
R 1
Selected Examples:
+ – BF 4
*
stereodivergent reaction
OPfp
O
MeO
N
N
Me
95%
>20:1 d.r., >99% ee
Scheme 27 Branch selective asymmetric α-allylation by Hartwig
Reprinted from the journal
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