The email said: “Across the street from your building/Black Mercedes.” It was a shining Saturday morning, and Jeffrey Deitch was parked by the curb with a chauffeur. The car seemed surprisingly flashy, a throwback to the Reagan ’80s. But Mr. Deitch, who resigned last year as the director of the Museum of Contemporary Art in Los Angeles, has permanently left the nonprofit realm. He is back in New York, buying and selling art again, and trying to keep up with pretty fast company.

At 62, Mr. Deitch is a diminutive, wiry man who was dressed in a purple suit and wearing his trademark goggly glasses.