反应详情

Particularly key to an efficient synthesis of 3-AP or 3-AMP is the high-yield introduction of a methyl or vinyl group, preferably vinyl, at the 2 position of the pyridine moiety utilizing a Heck or Stille vinylation reaction or a methylation reaction under Suzuki conditions. These reactions proceed at the 2-position of a pyridine moiety in high yield (generally, greater than 50% and in most instances, greater than 70%). The advantage of the vinylation reaction is that the 2-vinyl group may be readily converted to a 2-carboxaldehyde group for further conversion to the 2-thiosemicarbazone using a high yield ozonolysis reaction conducted in a polar solvent, such as methanol. The preferred vinylation reaction is a Heck or Stille vinylation reaction performed utilizing a reagent selected from among the following: Bu3SnCH=CHR3, (OH)2B--CH=CHR3, ClZnCH=CHR3 and XMgCH=CHR3. The vinylation reaction takes place in the presence of triphenylphosphine (PPh3) and/or tetrakis(triphenylphosphine) palladium [Pd(PPh3)4 ] usually in a solvent such as toluene in the presence of heat. The advantages of the methylation reaction under Suzuki conditions over the two step methylation of the prior art include a greatly improved yield, reduction in the number of steps and therefore handling required and ease in scaling the synthesis up for commercial production. Alternatively, to introduce a vinyl group at the 2-position of 3-nitropyridine, one may advantageously react 2-methyl-3-nitropyridine with dimethylforamamidedimethylacetal (DMFDMA) to produce 2-dimethylamino vinyl-3-nitropyridine compound 3a, followed by oxidation with sodium periodate (NaIO4) to produce carboxaldehyde 4 in an unexpectedly high 84% yield.

1. customParticularly key to an efficient synthesis of 3-AP or
2. customa Heck or Stille vinylation reaction
3. customa methylation reaction under Suzuki conditions
4. customin high yield (generally, greater than 50%
5. customThe advantage of the vinylation reaction
6. customa high yield ozonolysis reaction
7. customThe preferred vinylation reaction
8. customa Heck or Stille vinylation reaction
9. customThe vinylation reaction
10. temperatureof heat
11. customThe advantages of the methylation reaction under Suzuki conditions over the two step methylation of the prior art
12. customthe synthesis up for commercial production