Are these sentences correct:
1) The man who had entered the party we didn't know how was now dancing with Jane.
2) The man who had entered the party we knew not how was now dancing with Jane.
Gratefully,
Navi
Original Post
Hello, Navi—Both (1) and (2) are ungrammatical. You have violated "island constraints" (generative-grammar jargon) by trying to extract the subject of the embedded question and put it at the front of the sentence. To clean up the mess, put the subject of the embedded question back in its original position:
(3) We did not know how the man who had entered the party was now dancing with Jane.