A scalable and operationally simple decarboxylative trifluoromethylation of (hetero)arenes with easily accessible C 6 F 5 I(OCOCF 3 ) 2 under photoredox catalysis has been developed. This method is tolerant of various (hetero)arenes and functional groups. Notably, C 6 F 5 I is recycled from the decarboxylation reaction and further used for the preparation of C 6 F 5 I(OCOCF 3 ) 2 . The combination of photoredox catalysis and hypervalent iodine reagent provides a practical approach for the application of trifluoroacetic acid in trifluoromethylation reactions.

In the presence of 2-MeImpC only. 4In the presence of 2-MeImpC and 2-MeImpG.the family of C-rich oligonucleotides that can be copied efficiently.We have now shown that runs of G residues may be present, but that A and T residues must be isolated from each other and from G residues. The sequences TT, GT, and TG are partial barriers to copying, and the sequences AT, TA, AA, GA, and AG are almost total barriers.The half-times of some of the reactions that we have studied are collected in Table I. They illustrate the relative rates of the most successful copying reactions. The incorporation of G after any of the four (isolated) bases is rapid. The incorporation of the three other bases after G is substantially slower. The slow rate of incorporation of U after G is already a substantial obstacle to observing efficient template reactions involving incorporation of U in our system. After 4 days the hydrolysis of the activated nucleotides is significant, so the incorporation of several isolated U residues in a product could only be accomplished by replenishing the supply of 2-MeImpU from time to time.There are other obstacles to copying, in addition to those revealed by the present studies. Intramolecular self-structure is one such obstacle. It is likely to be particularly important for copolymers that include large proportions of both C and G. Another obstacle is the aggregation of G-rich copolymers via the formation of tetrahelical segments.A minimal self-replicating system consists of two complementary sequences each of which is capable of facilitating the synthesis of the other. Is such a system possible within the framework of our model system? Clearly a copolymer of C and G cannot qualify. If the two complements contain roughly equal amounts of C and G they are disqualified because they give rise to extensive intramolecular self-structure. If one polymer is rich in C, the other must be rich in G and so is disqualified because it forms a stable intermolecular tetrahelical self-structure.Can the introduction of isolated A and T residues save the situation? This seems unlikely, but one cannot be sure without more experimental information on the efficiency of templatedirected synthesis on oligoG sequences that contain an isolated A or T residue, for example, -GGAGGand related sequences.We are accumulating the information needed to answer this question. Experimental SectionMaterials. The sources of all reagents, and all experimental procedures, were the same as those reported in earlier papers of the series.1,2 Acknowledgment. This work was supported by Grant NAWG-1660 from the National Aeronautics and Space Administration. We also thank Aubrey Hill for technical assistance and Sylvia Bailey for manuscript preparation.

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EV-EMO system. CEMO(1–8) 0, 0.4, 1.0, 1.5, 2.3, 3.2, 3.8, 4.2 μg mL−1; CEV: 1.2 × 10−5 mol L−1; pH 7.0.