Fifty years ago this spring, Stanley Kubrick’s confounding sci-fi masterpiece, “2001: A Space Odyssey,” had its premières across the country. In the annals of audience restlessness, these evenings rival the opening night of Stravinsky’s “Rite of Spring,” in 1913, when Parisians in osprey and tails reportedly brandished their canes and pelted the dancers with objects. A sixth of the New York première’s audience walked right out, including several executives from M-G-M. Many who stayed jeered throughout. Kubrick nervously shuttled between his seat in the front row and the projection booth, where he tweaked the sound and the focus. Arthur C. Clarke, Kubrick’s collaborator, was in tears at intermission. The after-party at the Plaza was “a room full of drinks and men and tension,” according to Kubrick’s wife, Christiane.