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Chapter-5
Synthesis of highly substituted pyrroles
5.9 Experimental section
Thin-layer chromatography was accomplished on 0.2-mm precoated plates of
silica gel G60 F 254 (Merck). Visualization was made with UV light (254 and 365nm)
or with an iodine vapor. IR spectra were recorded on a FTIR-8400 spectrophotometer
using DRS prob. 1 H (300 MHz), 1 H (400 MHz), 13 C (75 MHz) and 13 C (100 MHz)
NMR spectra were recorded on a Bruker AVANCE II spectrometer in CDCl 3 and
DMSO. Chemical shifts are expressed in δ ppm downfield from TMS as an internal
standard. Mass spectra were determined using direct inlet probe on a GCMS-QP 2010
mass spectrometer (Shimadzu). Solvents were evaporated with a BUCHI rotary
evaporator. Melting points were measured in open capillaries and are uncorrected.
Synthesis of 2-phenylacetyl chloride 107 (2).
In a 250mL round bottom flask equipped with magnetic stirrer and
thermometer was placed phenylaceticacid (0.2mol) in MDC (100 mL). To this, slowly
added a solution of thionyl chloride (0.25mol) in MDC (25 mL) under nitrogen
atmosphere. The reaction mixture was stirred for 2 hrs. The progress of reaction was
monitored by thin layer chromatography. After completion, the reaction mixture was
evaporated to dryness under vacuum and the residue directly used for next step.
Synthesis of 1-(4-fluorophenyl)-2-phenylethanone (3).
In a 250mL round bottom flask equipped with magnetic stirrer and
thermometer was placed 2-phenylacetyl chloride (2, 1 mmol) and ZnO (powder, 0.5
mmol) under nitrogen atmosphere. Slowly added fluorobenzne (1 mmol) in to
reaction mixture at room temperature. Color (usually pink, but in few cases green or
blue) developed immediately and darkened with progress of the reaction. The reaction
mixture was kept at room temperature with occasional stirring for 1 h to complete the
reaction (monitored by TLC). The solid mass was then eluted with dichloromethane
(20 mL) and the dichloromethane extract was then washed with an aqueous solution
of sodium bicarbonate and dried over anhydrous sodium sulfate. Evaporation of
solvent furnished practically pure the corresponding product with 90 % yield. 108
Department of Chemistry, Saurashtra University, Rajkot-360005 177