Interestingly, the distinct photoredox properties of CD-2 indeed exerted a significant impact on photocatalytic reaction activity (Fig. ). Under identical reaction conditions, using CD-2 as the photocatalyst, the major reaction product of substrate 1 was identified as the dehydrogenative annulation product 25 in up to 72% yield, while the Giese radical addition product 4 was obtained with less than 20% yield (Fig. ). This represents a rare and noteworthy catalytic activity, as dehydrogenative cross coupling products are less commonly observed in similar radical-mediated processes (ref 52). Control experiments conducted in the dark, without CD-2 or HAT catalyst, showed no conversion of substrates, confirming the necessity of both the photocatalyst and HAT catalyst for the reaction. In contrast, CD-1 photocatalyst, when combined with various weak acid/base combinations, did not yield any detectable cyclization products. Attempts to generate dehydrogenative annulation products using a combination of CD-1 with different adducts or HAT agents were also unsuccessful (table ). To our surprise, unlike other cyclization reaction mediated by C-H or N-H bond addition to cyano-or thiocyano-groups (ref , optimization of reaction conditions with either acid or base cocatalysts did not lead to any improvement on reaction yields. With the same HAT catalyst, the C-H bond activation selectivity of the CD-2 system remained consistent with that of CD-1, strongly favoring activation of N-alkyl C-H bonds, and competition at the benzylic positions was not observed (Fig. ). The desired pyrrole products were obtained in excellent to moderate yields for all N-mono-alkylated anilines (34 to 55). As with CD-1 catalysis, the reactions exhibited tolerance to halides and remote free carboxylic acids, although the yields significantly dropped when the anilines became electron deficient . Interestingly, such annulation methodology also offered good to moderate yields when applied to bicyclic substrates (46 to 48, and 54), which may give new insights to the synthesis of multi-substituted pyrrole-based bioactive molecules or pharmaceutical intermediates.