Fig. 6: Control experiments and mechanism studies.

a 1,4-enyne allylic alcohol as substrate. b 1,4-dienyl allylic alcohol as substrate. c monoallylic alcohol as substrate. d Deuterium experiment. e The coversation of compound 48 in different time periods. f Both Q9 and SiO2 accelerate (–)–36‘ conversion to allene (–)–36. g (–)–36‘ in the condition of base or CH2Cl2.