“…When the distance between the carbonyl and the olefin moieties was varied with different carbon chain linkers ( 1′ , Scheme a), the reaction outcomes changed vastly. γ,δ-Olefin ketone ( n = 1) gave the 3,4-dihydro-2 H -pyran 4 , presumably via a 6- endo - trig cyclization process similar to what was reported by Schindler and co-workers, while δ,ε-olefin ketone ( n = 2) gave the normal COM products ( 2a and 2a′ ). ε,ζ-Olefin ketone ( n = 3), on the other hand, did not convert to any cyclized products (see page S19 in the SI for more unproductive ε,ζ-olefin ketone substrates)…”