Patent ID: 8389531

Claim:
A process for the preparation of erlotinib or a pharmaceutically acceptable salt thereof substantially free of N-methoxyethyl impurity, wherein the N-methoxyethyl impurity is N-[(3-ethynylphenyl)-(2-methoxyethyl)]-6,7-bis(2-methoxyethoxy)-4-quinazolinamine, comprising dissolving crude erlotinib or a crude pharmaceutically acceptable salt of erlotinib in a solvent medium comprising dimethyl sulfoxide and an alcoholic solvent, and isolating erlotinib substantially free of N-methoxyethyl impurity from the solvent medium, wherein the erlotinib substantially free of N-methoxyethyl impurity has less than 0.1 wt % of N-methoxyethyl impurity.