In 1938, he tied for 3rd-4th in Kraków (POL-ch elim; Izak Schaechter won). After World War II, he played six-times in Polish championships (1946–1953). His best achievement was a 3rd-4th place at Sopot 1946 (Bogdan Śliwa won).
In tournaments, he tied for 9-10th at Warsaw 1947 (Svetozar Gligorić won), took 18th at Szczawno Zdrój (Salzbrunn) 1950 (Paul Keres won), and tied for 15-16th at Międzyzdroje 1952 (Milev and Balanel won).
Grynfeld represented Poland in 10th Chess Olympiad at Helsinki 1952, winning the silver medal at second reserve board (+5 –1 =4) there. He also played for Poland in friendly matches: POL–CSR at Katowice 1949, POL–HUN at Warsaw 1949, and POL–HUN–GDR at Görlitz 1952. He later emigrated to Israel.