Table 1 Screening of the reaction conditions^a,b.

Note: It is necessary to use freshly prepared 4-methylbenzenesulfonyl iodide in all the reactions. Compound 4 formation can be inhibited by carefully monitoring the reaction time.
^aReaction conditions, unless otherwise noted: 1a (0.10 mmol), 2a (0.11 mmol), and DCM (0.05 M) were stirred at 28 °C (The fluctuation (depends on local atmosphere) under irradiation with a 40 W Kessil blue LED lamp (Kessil A160WE Tuna Blue controllable LED aquarium light, λ_max = 462 nm flanked by a second peak at λ = 382 nm; more information can be found at Kessil.com) and cooled with a fan, and the reaction mixtures were placed ~8.5 cm from the LED light; 50% intensity of blue light was used.
^bIsolated yields.
^c0.1 M DCM was used.
^d1.5 equiv of 2a was used.
^eStirred at room temperature in the absence of a light source for 5 min.
^fStirred at room temperature in the absence of a light source for 24 h.
^gStirred under a nitrogen atmosphere.
^hStirred at 28 °C under heating in absence of light source.
ⁱ40 W PR160L-456 nm blue LED lamp was used (no second emission peak at <400 nm).

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