FlowSyn™ Application Note 12:
Condensation Reaction
O
O
NaOH - EtOH.
O
O
Ph
+
Ph
Ph
Ph
Ph
90oC
Ph
Ph
3
2
1
Ph
Objective:
Simple base-mediated condensation/dehydration reactions can be conveniently performed under
continuous flow-through conditions. In this example, the product 3 is intensely purple coloured
and its gradual formation can be easily seen using a transparent coil reactor.
Method:
System solvent:
Stock solution A:
Stock solution B:
Ethanol
Benzil 1 (0.60 g, 2.86 mmol, 0.14M) and diphenylacetone 2 (0.60 g, 2.86
mmol, 0.14M) in ethanol (20 mL)
0.25M Sodium hydroxide (0.2 g, 5 mmol) in ethanol (20 mL)
A fixed back-pressure regulator was fitted (75 psi) and this was used in all experiments.
a. Flow Optimisation using ‘Manual Control’ Interface
1.FlowSyn™ was fitted with a 2.8 mL perfluoropolymer (PFA) tubing reactor cassette, and the
heating unit was tensioned to ensure optimal thermal contact.
2.The two solutions were reacted continuously in the microreactor with 5 min retention time at
90ºC.
Reactors:
Coil Type:
Coil Temp:
Col. Temp:
Inlet A:
Inlet B:
Coil
Other 2.8 mL
90 °C
0°C
Bottle
Bottle
Reaction Time:
Total Flow Rate:
Volume A:
Volume B:
A:B Ratio:
5.00 min (00:05:00)
0.56 mL/min
2.0 mL
2.0 mL
1:1
3.After collection of 4 mL of reaction solution the solvent was evaporated giving a crude yield of
tetraphenylcyclopentadienone (89 mg, 80%) which was found to be relatively free of impurities
by TLC.
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