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13th July 2012 @ 02:10
Coupling of 4-F aryl pyrrole acid chloride and secondary amine side chain PMY 53-2.

PMY55-1.png

Reaction Start Time: 10.30 13/07/12
JRC 2-1 (250 mg, 1.1 mmol, 1 equiv.) was stirred in PhMe (2 mL) at room temperature. Thionyl chloride (0.16 mL, 2.1 mmol, 2 equiv.) was added. After 4 hours, the reaction was concentrated and triturated with hexane (8 mL) and concentrated again to a yellow solid. The acid chloride was dissolved in THF (8 mL). Crude PMY 53-2 (142 mg), DIPEA (0.40 mL, 2.30 mmol, 2.1 equiv.) and 4-DMAP (a few crystals) were stirred in THF (2 mL). The acid chloride was added dropwise and the mixture stirred over the weekend (2.5 days). TLC shows reaction complete. Reaction mixture adsorbed onto silica (dry-loaded) and purified by chromatography on silica (2-4% MeOH/DCM) gave 2 fractions; PMY 55-1-A, single spot by TLC, white foam (44 mg, 14%), mixed 2 spots by TLC PMY 55-1-B, colourless viscous oil (112 mg).

PMY 55-1-A; consistent with expected product by 1H and 13C NMR (though with some rotameric carbons).

PMY 55-1-B consistent with expected product and impurity observed in PMY 53-2.

TLC (10% MeOH/DCM) visualised with UV and vanillin:
2.5 days
Column TLCs


NMR:
1H, 13C, 19F NMR PMY 55-1-A


See also:
Hydrogenolysis of benzyl protected amine PMY 51-2 (PMY 53-2)
Hydrolysis of Ethyl 1-(4-fluorophenyl)-2,5-dimethyl-1H-pyrrole-3-carboxylate (JRC 2-1)
Synthesis of TCMDC-123812 via acid chloride (PMY 10-6)

Risk and Hazard Assessment:
See: Synthesis of TCMDC-123812 via acid chloride (PMY 10-2)
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Scheme
2.5 days
Column TLCs
1H, 13C, 19F NMR PMY 55-1-A
1H NMR
1H NMR PMY 55-1-B