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18th November 2016 @ 19:12

Reaction Scheme

scheme1.jpg

 

Reagents used

Reagents

Equivalence
corrections

Quantity
(mg / mL)

mmol

Molecular Weight

2-Bromobenzaldehyde

1

200 mg
0.13 mL

1.08

185.02

Toluene

-

5 mL

47.21

92.14

Pyrrolidine

 

2.6

200 mg
0.24 mL

2.81

71.12

Rac-BINAP

 

0.009

6.20 mg

9.96x10-3

622.67

CsCO3

 

0.8

282.00 mg

0.86

325.82

Pd(OAc)2

 

0.008

2.00 mg

8.91x10-3

224.51

DCM

-

70 mL

 

 

 

Procedure

To 2-bromobenzaldehyde (200 mg, 1.08 mmol) in toluene (5 mL) was added pyrrolidine (0.24 mL, 2.81 mmol), rac-BINAP (6.20 mg, 9.96x10-3 mmol), CsCO3 (282.00 mg, 0.86 mmol) and Pd(OAc)2 (2.00 mg, 8.91x10-3 mmol) sequentially. The reaction was purged with N2for 15 minutes, then heated for 21 hours at reflux. 

After this time, TLC analysis (50% EtOAc/pet. Ether) was undertaken. It could be seen that starting material was still present, but the reaction was quenched anyway. The reaction was poured onto half-saturated K2CO3 solution, and extracted into CH2Cl2. The combined organic phases were washed with brine, dried (MgSO4), filtered and the solvent removed in vacuo to give an orange oil (343 mg). 1H NMR showed that the reaction was a complex mixture, still containing starting material therefore an alternative route was sought. 

 

BH-nitro-reflux.jpg

Leaving the reaction mixture to reflux under inert nitrogen atmosphere. 

 

BH-reflux.jpg

Mixture left to stir and reflux for 21 hours.

 

BH-reflux-end.jpg

After refluxing for 21 hours, 35 minutes. A change in colour was noticed as it turned to dark brown with residue. 

 

BH-TLC.jpg

Third TLC plate under 50-50% mobile phase: after the use of more dilute 2-bromobenzaldehyde a better separation was seen under UV (254nm)

 

BH-organic phases.jpg

Extracted combined organic phases that was rotary evaporated

 

Analysis: 

1H NMR data of end product 

NA-01-001.jpg

 

References


Constantin Rabong, Christian Hametner and Kurt Mereiter, et al., Heterocycles, 2008, 75, 813.

 

Attached Files