The signals are totally incompatible. HDMI is digital, transmitting both video and audio through TMDS channels. Composite video is analog, based on how a tube TV scans, and does not include audio. You need a converter to convert between the two, not a simple pin adapter.
A possible exception is if you have some equipment that routes composite video and analog through an HDMI cable. I haven't heard of this specifically, but I know some projectors used the DVI or VGA port to input composite or component video. Judging by your question, I don't think this is what you're looking for.