Ray Yadidi, a frequent partner of Isaac Chetrit, is planning a 15-story office building on a vacant Garment District site, sources told The Real Deal. Yadidi’s Garment District-based investment firm Sioni Group is expected to file plans with the city’s Department of Buildings next week for a 65,000-square-foot property at 44 West 37th Street, located between Fifth and Sixth avenues.