DMPS-Pt/AC-CP

DMPS-Pt/AC-CP is a dimethylpolysilane (DMPS)-modified platinum catalyst supported on activated carbon (AC) and calcium phosphate (CP), which can be performed selective reduction of nitro groups and alkenes under liquid-phase continuous-flow conditions.

• A novel dimethylpolysilane-modified Pt catalyst, supported on a mixture of activated carbon (AC), and calcium phosphate (CP).
• Application for selective hydrogenation of nitro compounds and alkenes.

Selective reduction of nitro groups under continuous-flow conditions¹

Examination of metal and second supports

In the reduction of 2-(p-chlorophenyl)nitromethane 1, DMPS-Pd/AC-CP and Pd/C fully reduced both chloro and nitro groups of 1 to give amine 2a (Table 1, entries 1 and 2), whereas DMPS-Pt/AC-CP reduced only the nitro groups to give amine 2b in high yields (Table 1, entry 3). The platinum catalyst with a different support than DMPS-Pt/AC-CP showed lower activity and selectivity (Table 1, entries 4 and 5).

Selective reduction of nitro group in the presence of benzyl ether

In the reduction of nitromethane 3 bearing benzyl ether, DMPS-Pd/AC-CP as a catalyst gave amine 4a reduced both nitro group and benzyl ether, while DMPS-Pt/AC-CP gave amine 4b reduced only the nitro group in high yield (Figure 1).

Synthesis of baclofen precursor

DMPS-Pt/AC-CP was applied to a part of the synthesis process (functional group selective reduction followed by cyclization) of the precursor 7 of baclofen 8 (Figure 2). Precursor 7 was obtained in 93-96% yield in 69 hours.

Reduction of alkenes under continuous-flow conditions¹

Selective reduction of carvone

The reduction of (R)-carvone 9 using DMPS-Pt/AC-CP as a catalyst under optimized conditions of flow reaction afforded the desired unsaturated ketone 10 in high yield without saturated ketone 11 from over-reduction of 10 (Figure 3).

Synthesis of (S)-phellandrene

DMPS-Pt/AC-CP was applied to the first step (selective reduction of (R)-carvone 9) in the synthesis of (S)-phellandrene 12 (Figure 4). Hydrazone formation of the reducted product followed by Shapiro reaction gave (S)-phellandrene 12 in 80% yield.

References

1. Ishitani, H., Furiya, Y., Kobayashi, S. : Chem. Asian J.,15, 1688 (2020).
2. Miller, S. J., Ishitani, H., Furiya, Y., Kobayashi, S. : Org. Process Res. Dev., 25, 192 (2021).