Are there alternatives to 2,4-dichloropyrido[2,3-d]pyrimidine in synthesis?

In some synthesis applications, alternatives to 2,4-dichloropyrido[2,3-d]pyrimidine may include other pyrimidine derivatives such as 4-chloropyrimidine or 2-chloropyrimidine. Additionally, isomers or analogs like 2,4-dichloropyrimidine may provide similar functionality. However, the choice of alternative reagents depends on specific reaction conditions and desired product properties. Care should be taken to ensure that any substitute meets the necessary chemical and regulatory requirements.