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7th April 2014 @ 01:36

Successful repeat synthesis of TM 4, to be carried on to TM 5-3 and then the 2-chloro-6-pyrazine carboxylate starting material. Crude yield 27.9 g, as a ~1:1 mixture of TM 4-3 and m-chlorobenzoic acid remaining from the m-CPBA oxidation.

 scheme

 

Exact repeat of Repeat synthesis of 3-(methoxycarbonyl)pyrazine 1-oxide (TM 4-2).

 

TM 2-2 (17.6 g, 128 mmol) was suspended in DCE (160 mL), then m-CPBA (29.0 g 85 %, 144 mmol, 1.13 eq) was added. The solution wasrefluxed overnight (~18 hours), by the end of which the reaction mixture was a yellow solution with white solid floating in it. The reaction mixture was diluted with DCM (400 mL), chilled over ice, then filtered to remove the precipitated m-chlorobenzoic acid. This was repeated several times, accompanied by the reduction of solvent volume under vacuum. Eventually, no more m-CBA would precipitate, and the solvent was removed to give crude TM 4-3 as a pale yellow solid. Yield: 27.9 g. By the NMR spectrum below, this seems to consist of ~1:1 ration of m-chlorobenzoic acoid remaining from the oxidation (fine triplet 8.06, doublet of triplets 7.97, doublet of triplets 7.56, triplet 7.40), and TM 4-3 (fine triplet 8.78, douoblet 8.59, doublet of doublets 8.26).

1H crude spectrum (CDCl3, 500 MHz)

TM 4-3 crude 1H CDCl3 500 MHz.pdf

TM 4-3.zip
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TM 4-3 crude 1H CDCl3 500 MHz.pdf
TM 4-3.zip
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