A new metal-free oxidative [2+2+1] heteroannulation of 1,7-enynes with thiocyanates for producing thieno[3,4-c]quinolin-4(5H)-ones is presented. This reaction employs benzoylperoxide (BPO) as the oxidant and sodium thiocyanate as the sulfur source to enable the formation of three chemical bonds, two C-S bonds and one C-C bond, in a single reaction, and represents a new, practical access to S-heterocycles with the avoidance of the use of metal catalysts and excess bases.