Process for preparing 3-hydroxymethyl chromen-4-ones

Details Process for preparing 3-hydroxymethyl chromen-4-ones Process for preparing 3-hydroxymethyl chromen-4-ones

2001-06-14

2002-02-19

Higel, Floyd D. (Department: 1626)

Organic compounds -- part of the class 532-570 series

Organic compounds

Heterocyclic carbon compounds containing a hetero ring...

C549S408000, C549S412000

Reexamination Certificate

active

06348605

ABSTRACT:

The present invention relates to 3-(hydroxymethyl)chromen-4-ones of general formula (I):
wherein R is hydrogen, halogen, alkyl having 1 to 4 carbon atoms or alkoxy having 1 to 4 carbon atoms optionally substituted by phenyl or halogen and to a new process for preparing said compounds.
The compounds of the present invention are useful as intermediates in the preparation of pharmaceuticals, such as those disclosed in WO 96/32389.
The processes in use for preparing the compounds of general formula (I) consist in:
a) Reduction of the corresponding 3-formylchromen-4-ones with NaBH
4
and AlCl
3
(Tetrahedron Letters, 1973, 1995
; Tetrahedron
, 1974, 3, 3553
; Chem. Pharm. Bull
., 1974, 22, 2959). These reactions have the inconvenience of resulting in a low yield.
b) Condensation of the corresponding 2-sulfinyl-acetophenones with two moles of HCHO and subsequent pyrolysis of the sulfoxide (
J. Het. Chem
., 1974, 11, 183). Unfortunately, there is a danger of explosion when sulfinylacetophenones are prepared on an industrial scale.
The process of the present invention consists in treating the compounds of general formula (II), wherein R is as defined for (I), with formaldehyde and catalytic amounts of basic compounds, as for example sodium acetate, followed by dehydration in an acid medium. Common mineral acids, such as hydrochloric acid, can be used as acidifying agents.
The compounds of general formula (II) are found in equilibrium with their open tautomer forms (II′) and (II″). (
Tetrahedron Letters
, 1984, ad, 5813). Both in II′ and in II″ R is defined as for the preceding structures.
In contrast to the previously described processes, the process of the present invention provides high yields and, in addition, the industrial preparation of precursors is easily produced.


REFERENCES:
patent: 2378573 (1945-06-01), Natta
patent: 3887584 (1975-06-01), Von Strandtmann et al.
patent: 5643927 (1997-07-01), Foguet et al.
patent: 9525733 (1995-09-01), None
Janos Borbely et al.; Tetrahedron, vol. 37, 1981, pp. 2307-2312.

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