In 1962 François Truffaut interviewed Alfred Hitchcock rather extensively.
About 12 hours of audio has been broadcast on french radio. You can listen to the 25 parts here.
In part 15 Hitchcock talks about "Rope" (I transcribed it myself, so please excuse any errors):
I don't know why I really indulged in the stunt, I can only call it a stunt, in "Rope".
The play played in its own time. It was continuous action from the moment the curtain went up and when it finished. And I got the idea, how can I technically treat this in a similar thinking, that the technique should play without a break... the presentation of the film.
In other words, there is no break anywhere in the storytelling, It starts at at seven-thirty and finishes about nine-fifteen. And I got this crazy idea of saying, well, maybe if I could do it in one shot, the whole film.
When I look back of course it's quite nonsensical, really, because I was breaking all my own tradition of using film, the cutting of film, to tell story.*
The interview about "Rope" is about 30 mins long, so if you want to learn more about the film, have a listen.
The late film critic Roger Ebert wrote this about "Rope":
Alfred Hitchcock called “Rope” an “experiment that didn’t work out,” and he was happy to see it kept out of release for most of three decades.