The special nucleobase recognition pattern of 5-aza-7-deazaguanine nucleosides makes them valuable for construction of homo purine DNA, silver-mediated base pairs, and expansion of the four letter genetic coding system. To widen the utility of 5-aza-7-deazaguanine nucleosides, side chains were introduced at position-7 of the nucleobase. As key compounds, 7-iodo nucleosides were synthesized. Nucleobase anion glycosylation of the iodo derivative of isobutyrylated 5-aza-7-deazaguanine with the bromo sugar of 2,3,5-tri-O-benzoyl-1-O-acetyl-d-ribofuranose gave the pure β-D anomeric N-9 glycosylation product (67%), whereas one-pot Vorbrüggen conditions gave only 42% of the iodinated nucleoside. The noniodinated nucleoside was formed in 84%. For the synthesis of 2′-deoxyribonucleosides, anion glycosylation performed with Hoffer’s 2′-deoxyhalogenose yielded an anomeric mixture (α-D = 33% and β-D = 39%) of 2′-deoxyribonucleosides. Various side chain derivatives were prepared from nonprotected nucleosides by Pd-assisted Sonogashira or Suzuki–Miyaura cross-coupling. Among the functionalized ribonucleosides and anomeric 2′-deoxyribonucleosides, some of them showed strong fluorescence. Benzofuran and pyrene derivatives display high quantum yields in non-aqueous solvents and solvatochromism. Single-crystal X-ray analysis of 7-iodo-5-aza-7-deaza-2′-deoxyguanosine displayed intermolecular iodo–oxygen interactions in the crystal and channels filled with solvent molecules.

The N/B frustrated Lewis pair (FLP) dihydrogen splitting product 10 undergoes a facile B(C6F5)3‐catalyzed regioselective trans‐1,2‐hydridoborate addition reaction to phenylacetylene to give the cis‐styryl‐containing ammonium/borate zwitterion 12. The B(C6F5)3‐catalyzed reaction of 10 with 1‐phenylpropyne proceeded analogously to give 13. The respective [B]/H− addition to styrene gave the corresponding [B]−CH2CH2Ph‐containing product 14 under mild conditions. We obtained evidence that the reaction is initiated by hydride migration between the two B centers involved and is then continued by hydride addition to the borane activated alkyne or alkene, respectively. The H2‐splitting product 4 derived from the ethylene‐bridged P/B FLP 3 reacted analogously with these alkynes and also with styrene under B(C6F5)3 catalysis to yield the respective alkenyl‐ or alkyl borate products. The new addition products were characterized by using XRD.