Synthetic chemistry with nitrous oxide

Abstract

This review article summarizes efforts to use nitrous oxide (N2O, 'laughing gas') as a reagent in synthetic chemistry. The focus will be on reactions which are carried out in homogeneous solution under (relatively) mild conditions. First, the utilization of N2O as an oxidant is discussed. Due to the low intrinsic reactivity of N2O, selective oxidation reactions of highly reactive compounds are possible. Furthermore, it is shown that transition metal complexes can be used to catalyze oxidation reactions, in some cases with high turnover numbers. In the final part of this overview, the utilization of N2O as a building block for more complex molecules is discussed. It is shown that N2O can be used as an N-atom donor for the synthesis of interesting organic molecules such as triazenes and azo dyes.

1‐Alkynyltriazenes as Functional Analogues of Ynamides

“…Ther egioselectivity of the products,w ith the triazene functional group next to the ester groups,w as confirmed by single-crystal X-ray analysis of ac rystal of 18 (for details see the Supporting Information). These results demonstrate that 1-alkynyltriazenes are compatible with as trong Lewis acid such as Sc(OTf) 3 .…”

“…Research in our laboratory is directed towards the development of useful synthetic procedures involving nitrous oxide (N 2 O, "laughing gas"). [3] Recently,w eh ave discovered that it is possible to prepare 1-alkynyltriazenes by reaction of lithium amides with nitrous oxide and alkynyl Grignard reagents. [4] This simple method allows access to av ariety of 1-alkynyltriazenes in good yields.W hile aromatic triazenes have been studied extensively in the context of synthetic organic [5] and medicinal chemistry, [6] thec hemistry of 1-alkynyltriazenes is completely unexplored.…”

“…To conclude,w eh ave started to examine the chemical reactivity of 1-alkynyltriazenes,which can be prepared easily by ar ecently developed method. [4] On purpose,w eh ave not performed ad etailed study on scope and limitations for one or two selected reactions.I nstead, we have examined different types of reactions in order to obtain af irst impression of the general reactivity.T he results show that 1-alkynyltriazenes are activated alkynes,w hich undergo av ariety of chemical transformations.T he reactivity observed so far is reminiscent of what has been reported for ynamides.T he extent of the similarity between 1-alkynyltriazene and ynamide reactivities needs to be examined in future studies, but it seems likely that the transformations reported herein are merely the tip of the iceberg with respect to possible reactions of 1-alkynyltriazenes.O ne interesting aspect of these reactions is the possibility to access triazenes,w hich would be otherwise difficult to synthesize.F or example,i ti s unlikely that the olefinic triazenes described above (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)can be prepared by the standard synthetic route for triazenes.I n view of the fact that aromatic triazenes have been investigated extensively as potential antitumor agents,i tw ill be interesting to perform biological tests with these new olefinic triazenes.Asecond noteworthy point is the intrinsic reactivity of triazene-containing compounds.D espite the fact that the relative stability of the compounds means that handling and purification (for example,b yc hromatography) are quite straightforward, it is possible to substitute the triazene functionality with other groups,a sd emonstrated by the formation of compounds 23-27.T aken together,o ur results suggest that 1-alkynyltriazenes should become valuable reagents for synthetic organic chemistry.…”

Steric‐Structure‐Dependent Gel Formation, Hierarchical Structures, Rheological Behavior, and Surface Wettability

“…[40][41][42][43][44][45] Molecular sterics tructure has received much attentioni n synthetic chemistry,b ut ignored in the field of supramolecular self-assembly,asi tonly can be clearly understood through theoretical calculations. [46][47][48][49] Because noncovalent interactions are the main force for supramolecular self-assembly,a ny tiny change in the molecular structure would affect the noncovalent interactions and further change the self-assembly process. When C, N, or Oa toms act as linkersi namolecule, they are often in as p 3 -hybridized state.…”

Synthesis of Azo Dyes from Mesoionic Carbenes and Nitrous Oxide

“…In continuation of our investigations about the chemistry of N 2 O, we recently observed that mesoionic and carbanionic N‐heterocyclic carbenes were able to capture N 2 O to give stable covalent adducts . These results prompted us to question whether the new N 2 O adducts could also be used to prepare azo dyes.…”