[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Tetrathiafulvalenes, oligoacenenes, and their buckminsterfullerene derivatives: the brick and mortar of organic electronics.

The effective use of ring strain has been applied to considerable advantage for the construction of complex systems. The focus here is directed towards cyclopropanes as building blocks for organic synthesis. Although thermodynamics should take the side of synthetic chemists, only a specific substitution pattern at the cyclopropane ring allows for particularly mild, efficient, and selective transformations. The required decrease in the activation barrier is achieved by the combined effects of vicinal electron-donating and electron-accepting moieties. This Review highlights the appropriate tools for successfully employing donor–acceptor cyclopropanes in ring-opening reactions, cycloadditions, and rearrangements.

A new golden age for donor-acceptor cyclopropanes.

Cyclization reactions of donor–acceptor (D–A) cyclopropanes are recognized as versatile methods for construction of carbocyclic and heterocyclic scaffolds. In the literature, many examples of these polarized cyclopropanes' reactivity with nucleophiles, electrophiles, and radicals are prevalent. Although intermolecular reactivity of donor–acceptor cyclopropanes is widely reported, reviews that center on their intramolecular chemistry are rare. Thereupon, this tutorial review focalizes on new intramolecular transformations of donor–acceptor cyclopropanes for cycloisomerizations, formal cycloadditions, umpolung reactions, rearrangements and ring-opening lactonizations/lactamizations from 2009 to 2013. Furthermore, the role of D–A acceptor cyclopropanes as reactive subunits in natural product synthesis is underscored.

Intramolecular donor–acceptor cyclopropane ring-opening cyclizations

This review summarizes research directed towards the formation of carbocyclic adducts from donor–acceptor cyclopropanes. The focus of the review is on annulation and cycloaddition reactions (both inter- and intramolecularly) mediated by Lewis or protic acid, bases, or thermal conditions. Rearrangements resulting in carbocycles and those reactions mediated by transition metal catalysis have been excluded.

Carbocycles from donor–acceptor cyclopropanes

Recent advances in ring-forming reactions of donor–acceptor cyclopropanes

Substituted cyclopropanes have found broad application in modern organic synthesis owing to the unique reactivity of the cyclopropane moiety. Cyclopropanes can often be considered as three-carbon analogues of C=C bonds. For example, alkenes and cyclopropanes react with strong electrophiles and various radicals. Both undergo the addition of hydrogen and can be oxidized at the a position. The reactivity of cyclopropanes with electron-withdrawing substituents is similar to that of electron-deficient alkenes. However, the cycloaddition reactions of alkenes and cyclopropanes are quite different. In particular, the thermal reactions of alkenes are represented mainly by [1+2], [3+2], and [4+2] cycloaddition processes; thermal [2+2] cycloaddition occurs in very specific cases only. In contrast, the most well known type of cyclopropane cycloaddition is the [2p + 2s] reaction with alkenes. As this reaction yields cyclopentanes, it can also be considered as a [2+3] cycloaddition. The scope of such [2+3] cycloaddition reactions has been expanded significantly through the use of donor–acceptor cyclopropanes. The presence of both electron-donating and electron-withdrawing substituents on the cyclopropane ring enables cycloaddition to various multiple bonds, including C=C, C=O, C=N, and C N bonds. The [4+3] cycloaddition of cyclopropanes with dienes (Scheme 1) has not been reported previously, although this

Donor–Acceptor Cyclopropanes as Three‐Carbon Components in a [4+3] Cycloaddition Reaction with 1,3‐Diphenylisobenzofuran

A general method for ring opening of various donor–acceptor cyclopropanes with the azide ion through an SN2-like reaction has been developed. This highly regioselective and stereospecific process proceeds through nucleophilic attack on the more-substituted C2 atom of a cyclopropane with complete inversion of configuration at this center. Results of DFT calculations support the SN2 mechanism and demonstrate good qualitative correlation between the relative experimental reactivity of cyclopropanes and the calculated energy barriers. The reaction provides a straightforward approach to a variety of polyfunctional azides in up to 91 % yield. The high synthetic utility of these azides and the possibilities of their involvement in diversity-oriented synthesis were demonstrated by the developed multipath strategy of their transformations into five-, six-, and seven-membered N-heterocycles, as well as complex annulated compounds, including natural products and medicines such as (−)-nicotine and atorvastatin.

https://chemistry-europe.onlinelibrary.wiley.com/doi/pdf/10.1002/chem.201500456

Ring Opening of Donor–Acceptor Cyclopropanes with the Azide Ion: A Tool for Construction of N‐Heterocycles

Investigations on mono-[2+1]-, -[2+2]-, -[2+3]-, -[2+4]-, and polycycloaddition to [60]fullerene are reviewed. The main reagents used in cycloaddition and the reaction mechanisms are surveyed. The possible applications of cycloadducts are considered. The review covers the investigations of the last five years as well as the most important earlier studies.

Cycloaddition to buckminsterfullerene C60: advancements and future prospects

The first example of (3+3)-annulation of two different three-membered rings is reported herein. Donor-acceptor cyclopropanes in reaction with diaziridines were found to afford perhydropyridazine derivatives in high yields and diastereoselectivity under mild Lewis acid catalysis. The disclosed reaction is applicable for the broad substrate scope and exhibits an excellent functional group tolerance.

Igor V. Trushkov

Papers

Recent advances in ring-forming reactions of donor–acceptor cyclopropanes

Donor–Acceptor Cyclopropanes as Three‐Carbon Components in a [4+3] Cycloaddition Reaction with 1,3‐Diphenylisobenzofuran

Ring Opening of Donor–Acceptor Cyclopropanes with the Azide Ion: A Tool for Construction of N‐Heterocycles

Cycloaddition to buckminsterfullerene C60: advancements and future prospects

(3+3)-Annulation of Donor-Acceptor Cyclopropanes with Diaziridines.