Pathways in the Degradation of Geminal Diazides

Reactions with Geminal Diazides: Long Known, Full of Surprises, and New Opportunities

Geminal diazides are uncommon yet powerful tools in organic synthesis. The chemistry of this class of functional compounds is characterized by quite unusual reactivities, including fragmentations and degradations, along with known reactions of organic azides. This Short Review highlights the major reactivities of various structural units having geminal diazido moieties, and provides an overview on the synthetic opportunities of such compounds.

1 Introduction

2 Preparation of Geminal Diazides

3 Reactivities of Geminal Diazides

3.1 α,α-Diazido Carbonyls

3.2 1,3-Diketones

3.3 Diazidated β-Ketoesters

3.4 Diazidated Malonates

3.5 Diazidated Malonamides

3.6 Miscellaneous Geminal Diazides

4 Conclusion

Dual Roles of Azide: Dearomative Dimerization of Furfuryl Azides

A dearomative dimerization of furfuryl azides for the construction of furfuryl triazoles is developed. As a rare leaving group, azide is capable of initiating the generation of a furfuryl cation under the Lewis acid-catalyzed conditions, followed by reacting with the other azide to realize an intermolecular [3 + 2] cycloaddition/furan ring-opening cascade. By extending the reaction time, a fragmentation reaction of resulting furfuryl triazoles occurs to afford 1H-triazoles in high yield. Control studies demonstrated that key furfuryl cations also can be obtained from furfuryl triazoles. Furthermore, a chemoselective cross-cycloaddition can be achieved between furfuryl azides and a benzyl azide.

Direct Synthesis of α-Fluoro-α-Triazol-1-yl Ketones from Sulfoxonium Ylides: A One-Pot Approach

The work reported herein showcases a new route to access α-fluoro-α-triazol-1-yl ketones from sulfoxonium ylides via α-azido-α-fluoro ketone intermediates. In a one-pot, two-step sequence, the ketosulfoxonium reactant initially undergoes insertion of F⁺ and N₃^-, followed by a subsequent CuAAC reaction with arylacetylenes to install a 1,4-triazolo moiety. The approach allows for modification to both the sulfoxonium ylide and arylacetylene reactants. Fifteen examples have been reported, with yields ranging between 22% and 75%.

Luminescent terpyridine appended geminal bisazide and bistriazoles: multinuclear Pt(II) complexes and AIPE-based DNA detection with the naked eye

We report square planar Pt(ii) complexes as luminescent biosensors for DNA detection in solution. The sensing is attributed to the aggregation induced bright red photoluminescence (AIPE) of the complexes in the presence of DNA that can be seen with the naked eye using only a 360 nm light source. Terpyridine appended luminescent geminal bistriazoles (L1-L4, from geminal bisazide A through azide-alkyne 'click' cycloaddition) with versatile chelating sites were explored for metal coordination and reaction with Pt(dmso)2Cl2 yielding tetranuclear and dinuclear complexes of Pt(ii) with different N∩N ligand environments. Thermally stable gem-bisazide and bistriazoles are hardly reported in the literature and this is the first report of terpyridine appended geminal bisazide and bistriazoles.

Rubazonic Acids and Their Synthesis

Rubazonic acids are a class of dyes that are long-known, but studies on their syntheses and uses are rare. We now describe an experimentally simple and highly practical one-pot procedure for their synthesis starting from easily accessible 1H-pyrazol-5(4H)-ones. This protocol provides direct access to a broad range of the desired rubazonic acid derivatives through oxidative diazidation combined with a reductive work-up, without the need to isolate the potentially hazardous diazido compounds generated en route the target compounds. We also show how more challenging variants of rubazonic acid are efficiently prepared using an alternative two-step procedure and controlled hydrogenation conditions.

Metal-Free C-N or C-C Bond Cleavages of α-Azido Ketones: An Oxidative-Amidation Strategy for the Synthesis of α-Ketothioamides and Amides

A novel metal-free oxidative-amidation strategy for the synthesis of α-ketothioamides and amides from α-azido ketones was developed. The C-H bond thionation of α-azido ketones with elemental sulfur could form α-ketothioacyl azide, which was then nucleophilically attacked by amines, causing the cleavage of the C-N bond to afford α-ketothioamides, while amides could be formed with the release of nitrogen gas and cyano anion in the presence of PhI(OAc)₂ by selective C-C bond cleavage.

A Synthetic Route Toward Tetrazoles: The Thermolysis of Geminal Diazides

A new synthetic route toward the tetrazole core is described, which is based on a general fragmentation pattern that was found in a range of compounds featuring geminal diazido units. Through a simple two-step procedure, the synthesis of structurally diverse target compounds containing a tetrazole, such as tetrazoloquinoxalinones, benzoylaryltetrazoles, tetrazolotriazinones, and tetrazoloazepinones, was easily accomplished, starting from broadly accessible substrates (i.e., oxindoles, diarylethanones, pyrazolones, and phenanthrols). The initial oxidative diazidation reaction with iodine and sodium azide under mild conditions is followed by the thermal fragmentation under microwave irradiation, leading to the tetrazole products. Noteworthy, an experimental solution is presented in which the potentially hazardous diazide intermediates are not isolated and the concentration of crude reaction mixtures containing diazides is not required to achieve the tetrazoles in good yields.