From: Uno Mäeorg (uno$##$chem.ut.ee)
Date: Sat Mar 20 2004 - 03:14:54 EST
We tried to prepare the 4-methoxy(dichloromethyl)benzene according to the
patent procedure EP0432818:
4-Methoxybenzaldehyde (5.0 g) in ether (50 ml) was added dropwise to
phosphorus pentachloride (3.6 mol.equiv.) stirred in dry ether (50 ml) at 0
DEG C; after 30 m, the cooling bath was removed, and the reaction was
followed by t.l.c. or n.m.r. until no starting material remained (30 m).
The products were filtered and the filtrate was concentrated to ca. 10 ml
at 14 mmHg and then treated with petrol (70 ml, b.p. 40 - 60) and allowed
to stand for 3 h. The solution was decanted from a dark oil which was
produced and quickly washed with ice water (2 x 100 ml), dried and
evaporated to give the dichloride. Yield: 80%; dH 7.6 (2H, d, J Hz), 7.0
(2H, d, J Hz), 6.8 (1H, s), 3.9 (3H, s).
We used perfect dry solvents and the new Aldrich bottle of PCl5.
Anisaldehyd was freshly distilled. Unfortunately the reaction doesn't
complete even after 1 and 2 hr (TLC). The final product contained anyway
the starting aldehyde spot and also large spot at the start.
Have somebody experience with such compounds. What could be the real
procedure what is going to work?
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