Table 4. Control experiments for preliminary mechanistic studies ^a .

Entry	Light	TMDAM	Additive	Conversion [%]	Yield of 3f [%]	Yield of 9 [%]
1	+	+	–	100	81	7
2	–	–	–	0	0	0
3	–	+	–	13	13	0
4	–	+	Bu3SnH	46	17	26
5	+	+	Bu3SnH	100	18	80
6	+	+	DHA	68	42	26 b
7	+	+	TEMPO	69	15	11

^aReactions were run in batch and yields were determined by ¹H NMR spectroscopic analysis with 1,3,5-trimethoxybenzene as an internal standard.

^b11% of anthracene was formed. TMDAM: N,N,N′,N′-tetramethyldiaminomethane; DHA: 9,10-dihydroanthracene; TEMPO: (2,2,6,6-tetramethylpiperidin-1-yl)oxyl.