cyclize
Concise Oxford English Dictionary © 2008 Oxford University Press:
cyclize /ˈsʌɪklʌɪz/ (or cyclise /ˈsʌɪklʌɪz/)
▶verb Chemistry undergo or cause to undergo a reaction in which one part of a molecule becomes linked to another to form a closed ring.
– derivatives
cyclization noun.
cyclization noun.
'cyclize' also found in these Oxford entries:

