Table 2. Control experiments to probe the PCET mechanism for DHP cleavage. PMP, para-methoxy phenyl.

Entry	R	Photocat.	E*ox, a	Base	pKa	Effective BDFE b	Yield c (%)
1	H	PC2	+0.97	[AcO]NBu4	12	94	33
2	H	PC2	+0.97	[TFA]NBu4	7	87	36
3	H	PC2	+0.97	[DBP]NBu4	5	84	41
4	H	PC2	+0.97	[BArF4]Na	<1	—	<5
5	H	PC2	+0.97	None	—	—	<5
6	H	PC5	+1.35	None	—	—	14
7	H	PC5	+1.35	[AcO]NBu4	12	102	21
8	Me	PC2	+0.97	[AcO]NBu4	12	94	<5
9	Me	PC5	+1.35	[AcO]NBu4	12	102	17

^a E*^ox in V.

^bBDFE in kcal mol^–1.

^cIsolated yield of purified product. Ac, acetyl. TFA, 2,2,2-trifluoroacetate. DBP, di(n-butyl)phosphate. BAr^F₄, tetrakis(3,5-bis(trifluoromethyl)phenyl)borate.