Pd(OAc)₂ (HPMC encapsulated)

• 2-Bromobenzaldehyde [B0836]
• Styrene [S0095]
• Potassium Phosphate Hydrate (= K₃PO₄) [T3998]
• Pd(OAc)₂ (HPMC encapsulated) [R0303]
• DMF

Pd(OAc)₂ (HPMC encapsulated) (one capsule) was added to a solution of 2-bromobenzaldehyde (925 mg, 5.0 mmol), tripotassium phosphate hydrate (1.59 g, 7.5 mmol, 1.5 eq.) and styrene (1.56 g, 15 mmol, 3.0 eq.) in DMF (5 mL) at room temperature and the reaction mixture was stirred at 150 °C for 3 hours. The solution was then diluted with ethyl acetate (15 mL) and sat. Na₂SO₄ aq. (15 mL), and filtered through Celite pad and the filtrate was extracted with ethyl acetate (15 mL x 2). The organic layer was washed with water (15 mL) and brine (10 mL), dried over sodium sulfate and concentrated under reduced pressure. The crude product was purified by silica gel chromatography (hexane:dichloromethane = 1:0 - 1:4) to afford (E)-2-styrylbenzaldehyde (880 mg, 85% yield) as a pale yellow oil.

The reaction mixture was monitored by GC.
The material of the capsule is water-soluble HPMC (hydroxypropyl methylcellulose).
The shape of the capsule is like the image below and Pd(OAc)₂ (ca. 500 μmol) is encapsulated in each capsule.

The capsule disintegrates as shown in the image below when stirred in the solvent for about 15 minutes, releasing its content.

(E)-2-Styrylbenzaldehyde

¹H NMR (400 MHz, CDCl₃); δ 10.33 (s, 1H), 8.06 (d, J = 16.0 Hz, 1H), 7.85 (d, J = 7.6 Hz, 1H), 7.74 (d, J = 8.0 Hz, 1H) 7,61-7.56 (m, 3H), 7.45 (t, J = 7.2 Hz, 1H), 7.41-7.38 (m, 2H), 7.33-7.29 (m, 1H) 7.07 (d, J = 16.0 Hz, 1H).

• Reagent and Catalyst Capsules: A Chemical Delivery System for Reaction Screening and Parallel Synthesis
  • N. Borlinghaus, B. Schönfeld, S. Heitz, J. Klee, S. Vukelić, W. M. Braje, A. Jolit, J. Org. Chem. 2021, 86, 1357.

• HPMC: A Biomass-Based Semisynthetic Sustainable Additive Enabling Clean and Fast Chemistry in Water
  • S. Sharma, T. N. Ansari, S. Handa, ACS Sustainable Chem. Eng. 2021, 9, 12719.