Patrombon, now ranked 1,186th in the pro circuit, advanced against second seed Guatemalan Christopher Diaz-Figueroa, who ousted another Mexican, Luis Carlos Vazquez, 6-0, 6-0.
Filipino-Italian Marc Reyes, who managed to get through the qualifying, bowed to Australian fifth seed Chris Letcher, 7-5, 6-2.
Meanwhile, Philippine Davis Cupper Treat Huey will team up with long-time partner Somdev Devvarman in the US Open men’s doubles.
They will take on Russians Igor Andreev and Igor Kunitsyu in the first round Thursday.
Andreev bowed out of the men’s singles to fifth seed David Ferrer of Spain, 2-6, 6-3, 6-0, 6-4.