A process for the preparation of pyrazine derivatives.

摘要

Aprocess for the preparation of a pyrazine derivative of formula I:
<Chemistry id="chema01" num="0001"><Image id="ia01" he="25" wi="67" file="IMGA0001.TIF" imgContent="chem" imgFormat="TIFF" inline="no" /></Chemistry>wherein R<Sub>1</Sub> represents hydroxy, C<Sub>1</Sub>-C<Sub>6</Sub> alkoxy or a group of formula NR<Sub>2</Sub>R<Sub>3</Sub>, wherein R<Sub>2</Sub> and R<Sub>3</Sub> are independently hydrogen or C<Sub>1</Sub>-C<Sub>6</Sub> alkyl or, R <Sub>2</Sub> and R<Sub>3</Sub> form together with the nitrogen atom to which they are linked, a ring which may contain one or more additional heteroatoms; which process comprises reacting a compound of formula II:
<Chemistry id="chema02" num="0002"><Image id="ia02" he="25" wi="69" file="IMGA0002.TIF" imgContent="chem" imgFormat="TIFF" inline="no" /></Chemistry>wherein R represents hydrogen, C<Sub>1</Sub>-C<Sub>6</Sub> alkyl or C<Sub>1</Sub>-C<Sub>6</Sub> alkoxy, Y represents hydrogen, sodium, lithium or potassium, and A is a nitrile group or a substituent of formual COR<Sub>1</Sub>, wherein R<Sub>1</Sub> is as defined above, either with pyruvic aldehyde oxime of formula III:
<Chemistry id="chema03" num="0003"><Image id="ia03" he="21" wi="68" file="IMGA0003.TIF" imgContent="chem" imgFormat="TIFF" inline="no" /></Chemistry>or with a pyruvic aldehyde oxime acetal derivative of formula IV:
<Chemistry id="chema04" num="0004"><Image id="ia04" he="26" wi="73" file="IMGA0004.TIF" imgContent="chem" imgFormat="TIFF" inline="no" /></Chemistry>wherein R<Sub>4</Sub> and R<Sub>5</Sub> are independently hydrogen or C<Sub>1</Sub>-C<Sub>6</Sub> alkyl or may be linked together in such a way that the compound of formula IV is a cyclic acetal; and when A is a nitrile group, hydrolyzing the reaction product; and, if desired, converting a compound of formula I so produced into another compound of formula I by a method known per se.