A.
cis,cis-Monomethyl muconate. A
1000-mL, three-necked, round-bottomed flask is equipped with a
mechanical stirrer and an
addition funnel ((Note
1),
f.htmig. 1). The flask is charged with
400 mL of pyridine,
5 mL (0.12 mol) of methanol and
9.9 g (0.10 mol) of cuprous chloride under an atmosphere of
nitrogen (Note
2). The resultant yellow solution is stirred vigorously at room temperature until the
cuprous chloride dissolves (Note
3). The
nitrogen is removed and
oxygen is bubbled into the flask below the surface of the liquid for approximately 30 min (Note
4). A solution, composed of
1000 mL of pyridine,
5.5 g (0.05 mol) of 1,2-dihydroxybenzene (catechol), and
5 mL (0.12 mol) of methanol, is degassed and slowly added to the flask over a 2-hr period with efficient stirring (Note
5). The reaction mixture is stirred for an additional 30 min before the
pyridine is removed at reduced pressure. The dark green residue is dissolved in
300 mL of ethyl ether (Note
6) and
300 mL of 6 N hydrochloric acid; this solution is stirred for 10 min and filtered over Celite, and the organic layer is isolated. The
ether is removed at reduced pressure and the resultant brown residue is boiled sequentially with six
50-mL portions of hexane (Note
7). The hot liquid is carefully decanted, leaving behind most of the dark residue. The yellow-to-colorless solid is crystallized from hot
hexane (or
methanol) to yield
5.6–6.2 g (
71–80%) of colorless needles, mp
80–81°C (Note
8).