Recent Advances of Cyclopropene Chemistry

Abstract

Cyclopropenes are the smallest unsaturated carbocyclic but readily accessible compounds with high strain energy (54.1 kcal/mol), which resulting in the high activity of cyclopropenes in reactions. Cyclopropenes have been a hot research topic for many years, since the synthesis, transformations, and applications of cyclopropenes have drawn attentions of chemists, and a series of interesting and significant cyclopropene chemistry have been demonstrated. Especially when transition-metal-catalysts were introduced into cyclopropene chemistry, a number of unprecedented transformations through addition reactions, cycloadditions, and ring-opening reactions have been developed. Several excellent reviews focused on transition metal chemistry of cyclopropenes and enantiomerically enriched cyclopropene have been published before 2011. However, some very important progresses on cyclopropene chemistry have been achieved in the next several years. This review will cover the literatures from 2011 to 2015, including the synthesis, transformations and applications of cyclopropenes. The paper included five chapters: the first part is the introduction of the article; in the second chapter, the recent advances in preparation of cyclopropenes were described; next, in the third part, the recent progress of transformations of cyclopropenes was discussed. The reactions of cyclopropenes were devided into two categories: 1) the transformations in which the ring of cyclopropene was opened by cycloaddition and cycloisomerization reactions. In some reactions an unsaturated metal carbene mechanism was involved, and subsequent insertion reaction, isomerization, or coupling reactions led to diverse functionalized products. In these reactions, cyclopropene serves as a very important 3-carbon building block; 2) the chemical transformations in which the three-membered ring was retained is an important pathway to multisubsitituted cyclopropane derivatives; the forth part summarized the recent applications of cyclopropenes, mainly focused on its specialities as bioorthogonal chemical reporters. Cyclopropene showed great significances in affinity-based protein labeling and synthesis of photo-cross-linkers suitable for live-cell imaging; in the last part, we summed up the article and made an outlook on the future development of cyclopropene chemistry.

Practical Peptide Synthesis Mediated by a Recyclable Hypervalent Iodine Reagent and Tris(4-methoxyphenyl)phosphine

“…Specifically, the reaction usually requires a high temperature (60 °C) and a long reaction time (6–9 h), and 4-(dimethylamino)­pyridine, which is toxic, is indispensable. As part of our ongoing interest in oxidation reactions induced by hypervalent iodine reagents and in peptide coupling reactions mediated by such reagents, we have now developed a more powerful iodosodilactone type reagent by introducing a 3,5-bis­(trifluoromethyl)­phenyl group at the position para to the iodine center. We designed the reagent on the basis of the following rationales: we expected (a) that the strongly electron-withdrawing trifluoromethyl groups would enhance the electrophilicity of the iodine­(III) center, thus resulting in increased reactivity, and (b) that the high liposolubility of the trifluoromethyl-substituted phenyl group would make the coupling reagent more soluble in organic solvents than the parent reagent.…”

Highly selective catalyst- and additive-free iodosulfonylation of cyclopropenes in water

“…In comparison with cyclopropanation methods from acyclic starting materials, 6,7 functionalization of the readily available cyclopropenes 8 is a more straightforward and general method where diverse polysubstituted cyclopropanes could be obtained from a single precursor (Scheme 2a). 8,9 Pioneering transition-metal-catalyzed approaches 9,10 have been well developed for incorporating a variety of functional groups, but the use of expensive or polluting transition metals and air-sensitive reagents has limited the application of these methods. On the other hand, radical addition to cyclopropenes 8,11 without the use of noble metals is economical, but sometimes hazardous initiators are used.…”

Synthetic Applications of Cyclopropene and Cyclopropenone: Recent Progress and Developments

“…[6] The cyclopropene derivatives undergo a variety of reactions such as ring-opening reactions, isomerization reactions, CÀ C coupling reaction, CÀ H activation, cycloaddition reactions, thermal and photo-irradiation reaction, acid-base catalyzed reactions under the influence of various chemical reagents, (electrophiles, nucleophiles, radicals, and organometallics) and external forces (heat and light). These findings were comprehensively reviewed and the major reviews reported by Carter [7] in 1964, Min Shi in 2011 and 2020, [8] Xu [9] in 2015, and Trindade [10a] in 2017 have also been published.…”