[1] Greenfield is the founding director and counsel of TEACH NYS,[2][3] and prior to his election served as the executive vice president of the Sephardic Community Federation.

[6] On January 7, 2010 Greenfield announced his candidacy on the Zev Brenner radio show to replace Simcha Felder in the 44th district, which included Bensonhurst, Borough Park, Gravesend, Kensington, Midwood, and Sheepshead Bay in Brooklyn.

[18] Greenfield authored a law that banned the Department of Sanitation from placing hard-to-remove stickers on vehicles that were parked on the wrong-side of the street.

[19] He co-authored a law that requires the Department of Education to notify parents and teachers about potentially harmful polychlorinated biphenyl (PCB) in classrooms.

[21] Greenfield's proposed legislation was adopted by the New York City Council Department of Finance as a pilot program in June 2012.

This legislation is the lynchpin of Vision Zero and is widely considered to be the key strategy behind saving lives by reducing traffic accidents in New York City.