From: samarium Steiner (neptunium$##$gmx.net)
Date: Tue Mar 23 2004 - 00:29:03 EST
they mention a quick washing wit ice water. this and my knowledge to
benzylic halides (ok, this is a dihalide) indicates for a decomposition (e.g.
hydrolysis, once one OH has substituted one chlorine, the compound loses HCl and
you may get again your aldehyde.
also TLC may be not the detection method of choice.
> Hi colleagues,
> 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
> 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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