4,5-Dicyanoimidazole: Synthesis Activation & Optoelectronic Applications

4,5-Dicyanoimidazole (C5H2N4) is an aromatic heterocyclic organic compound featuring a five-membered imidazole ring substituted with two cyano groups at the 4- and 5-positions. 4,5-Dicyanoimidazole may be used to synthesize novel imidazo diazepine analog and N-benzyl-4,5-dicyanoimidazole.

Efficient activation of nucleoside phosphoramidites with 4,5-dicyanoimidazole

Oligonucleotides and modified oligonucleotides are of great interest as therapeutic candidates, either as inhibitors of gene expression, or as inhibitors of protein function. This increased interest requires oligonucleotide preparation in ever larger amounts. How ever, the large scale synthesis of RNA and modified RNA oligonucleotides in particular continues to pose a formidable challenge. The synthesis of oligonucleotides from nucleoside 3′-N,N-diisopropylphosphoramidites is a common practice. Activation of the phosphoramidites for coupling to a 5′-hydroxyl group of an oligonucleotide is usually achieved by addition of 1H-tetrazole. While this activator is the accepted standard for coupling of deoxynucleoside phosphoramidites, alternatives are often sought for coupling of more sterically hindered nucleoside phosphoramidite monomers. Activation with 4,5-Dicyanoimidazole proved the most efficient way to assemble oligonucleotides containing 2′-deoxy-2′-aminopyrimidines. A typical preparation of a 2′-aminopyrimidine-containing modified oligonucleotide, oligonucleotide 3 (sequence given in Materials and Methods), of 36 nt length with 4,5-Dicyanoimidazole activation. This oligonucleotide is unique since it not only contains 2′-aminopyrimidines, but also a mixture of 2′-O-methylpurines, ribopurines and a stretch of 3′- and 5′-terminal phosphorothioate linkages. Conversely, activation with tetrazole did not give satisfactory yields.[1]

Since it is known that nucleophilic attack at the O6 position of guanosine followed by deprotection in ammonia results in formation of 2,6-diaminopurine contamination, it was important to test whether 4,5-Dicyanoimidazole is nucleophilic enough to undergo this reaction. For this purpose a 28mer oligodeoxynucleotide was prepared with DCI activation and deprotected in concentrated ammonia. An enzymatic digest of the crude product to its nucleoside components did not show contamination by 2,6-diaminopurine. In addition to activation of nucleoside phosphoramidites during coupling to oligonucleotides, activation with DCI is also useful in phosphitylation of nucleosides with 2-cyanoethyl tetraisopropyl phosphorodiamidite. 5′-DMT-thymidine was efficiently converted to the 3′-(2-cyanoethyl)-N,N-diisopropylphosphoramidite derivative using 4,5-Dicyanoimidazole. We have shown that phosphoramidite coupling during oligo nucleotide synthesis proceeds rapidly and with no observable side reaction when DCI is used as the coupling activator. This activator increases the rate of coupling in comparison with tetrazole while being less acidic. It is highly soluble in acetonitrile and thus allows for higher effective concentrations of nucleoside phosphoramidites during solid phase synthesis. A higher effective concentration in turn allows for lower phosphoramidite excess during coupling. Finally, the utility of 4,5-Dicyanoimidazole is not only recognized in oligonucleotide synthesis, but also in the preparation of nucleoside phosphoramidites from 3′-hydroxylnucleosides and bis-(N,N-diisopropyl)-2-cyano ethyl phosphoramidite.

Calculation of 4,5-dicyanoimidazole derivatives in solution

The search for advanced optical materials through rational design is a key focus in modern materials science, particularly in the development of π-conjugated organic compounds for organic electronics and optoelectronics. There has been a concerted effort to establish structure–property relationships to achieve large nonlinear optical (NLO) responses. In this study, we report solvent effects on the geometry, absorption spectrum, and first hyperpolarizability of a set of push–pull molecules with a 4,5-dicyanoimidazole acceptor (A) unit (DCI), a N,N-dimethylamino donor (D) group (NMe2), and progressively larger π-conjugated systems, whose synthesis was reported. Previous studies have demonstrated that the β values of such push–pull molecules can be tailored by modifying the donating character of substituent groups, as well as by extending the π-conjugated system. We conduct an investigation on the impact of solvents in the geometry, absorption spectrum, and first hyperpolarizability of six molecules containing a 4,5-dicyanoimidazole acceptor unit and a N,N-dimethylamino donor group, with systematically extended π-conjugated systems. Our study involved the use of all-atom sequential Monte Carlo simulations in combination with the average solvent electrostatic configuration and the free energy gradient methods under normal thermodynamic conditions to optimize the geometry of each molecule in four different solvents: dichloromethane, methanol, water, and formamide.[2]

References

[1]Vargeese C, Carter J, Yegge J, Krivjansky S, Settle A, Kropp E, Peterson K, Pieken W. Efficient activation of nucleoside phosphoramidites with 4,5-dicyanoimidazole during oligonucleotide synthesis. Nucleic Acids Res. 1998 Feb 15;26(4):1046-50. doi: 10.1093/nar/26.4.1046. PMID: 9461466; PMCID: PMC147346.

[2]Brand?o, Idney et al. “Calculation of the geometry, absorption spectrum, and first hyperpolarizability of 4,5-dicyanoimidazole derivatives in solution. A multiscale ASEC-FEG study.” The Journal of chemical physics vol. 161,3 (2024): 034503. doi:10.1063/5.0215931

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