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Abstract Palladium‐catalyzed aryl amination and Heck arylation reactions are complementary transformations, generally requiring a suitable catalyst combination and a base. With substrates containing both an amino group and a vinyl moiety, control of C─N versus C─C reactivity can lead to regiodivergent functionalizations. With this focus, reactions of silyl‐protected 8‐vinyl 2'‐deoxyadenosine and adenosine with aryl bromides and iodides have been studied. Pd(OAc)2, Pd2(dba)3, and preformed dichloro[1,1′‐bis(di‐t‐butylphosphino)ferrocene]palladium (II) (Pd‐118) were evaluated as metal sources. Ligands tested were Xantphos, DPEphos, BIPHEP, and DPPF, with Cs2CO3and K3PO4as bases. In toluene as solvent, the Pd(OAc)2/Xantphos/Cs2CO3combination was uniquely capable of predominantN6arylation. Aryl bromides and iodides gave comparable product yields. Replacement of Cs2CO3with K3PO4redirected arylation from the nitrogen atom to the vinyl carbon atom, and all other catalyst, ligand, and base combinations gave Cvinylarylation as well. Simply switching from Pd(OAc)2to Pd2(dba)3resulted in loss of theN6‐selectivity and Cvinylarylation was favored. Based upon these results, using two structurally similar catalytic systems sequential CvinylandN6arylations of the nucleosides were accomplished. Some of the products were converted to other novel nucleoside analogues. Because some compounds were fluorescent, their photophysical properties were assessed experimentally and computationally.
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Cyclic Diaryl λ 3 ‐Bromanes as a Precursor for Regiodivergent Alkynylation Reactions
Abstract Regiodivergent reactions are a fascinating tool to rapidly access molecular diversity while using identical coupling partners. We have developed a new approach for regiodivergent synthesis using the dual character of hypervalent bromines. In addition to the recently reported reactivity of hypervalent bromines as aryne precursors, the first transition metal‐catalyzed reaction is reported. Accordingly, the development of these two complementary transformations allows for the alteration of regioselectivity to furnish bothortho‐ andmeta‐substituted alkynylation products. Mechanistic and computational studies show how these selectivities are controlled.
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- Award ID(s):
- 2153972
- PAR ID:
- 10494333
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Angewandte Chemie International Edition
- Volume:
- 63
- Issue:
- 16
- ISSN:
- 1433-7851
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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