Dimethyl cubane-1,4-dicarboxylate

Irngartinger, Hermann; Strack, Stefan

doi:10.1107/s0108270194004634

Cited by 3 publications

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References 9 publications

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“…The structure of 26 (1,4‐dimethoxycarbonyl‐cubane) preserves the motif seen in 18 but this time it is twofold on both sides of the cubane scaffold (Figure F) . However, by simply substituting one side of the cubane scaffold with a methyl ether ( 24 ) O 2 becomes the dominant side at which the cubane hydrogen atoms interact with the ester moiety .…”

Section: Resultsmentioning

confidence: 99%

Not Your Usual Bioisostere: Solid State Study of 3D Interactions in Cubanes

Flanagan

Bernhard

Plunkett

2019

Chemistry A European J

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Previous studies by Desiraju and co‐workers have implicated the acidic hydrogen atoms of cubane as a support network for hydrogen bonding groups. Herein we report a detailed structural analysis of all currently available 1,4‐disubstituted cubane structures with an emphasis on how the cubane scaffold interacts in its solid‐state environment. In this regard, the interactions between the cubane hydrogen atoms and acids, ester, halogens, ethynyl, nitrogenous groups, and other cubane scaffolds were cataloged. The goal of this study was to investigate the potential of cubane as a substitute for phenyl. This could be achieved by analyzing all contacts that are directed by the cubane hydrogen atoms in the X‐ray crystal structures. As a result, we have established several new cubane interaction profiles, such as the catemer formation seen in esters, the preferences of halogen–hydrogen contacts over direct halogen bonding, and the stabilizing effects caused by the cubane hydrogen atoms interacting with ethynyl groups. These interaction profiles can then be used as a guide for designing cubane bioisosteres of known materials and drugs containing phenyl moieties.

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Section: Resultsmentioning

confidence: 99%

Not Your Usual Bioisostere: Solid State Study of 3D Interactions in Cubanes

Flanagan

Bernhard

Plunkett

2019

Chemistry A European J

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The Cubane Cage – A Sensitive Probe for Assessing Substituent Effects on a Four-Membered Ring, Part II

Irngartinger¹,

Strack

Gredel

et al. 1999

Eur. J. Org. Chem.

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The crystal structures of methyl 4‐methoxycubane‐1‐carboxylate (1), 1‐acetamido‐4‐fluorocubane (2), methyl 4‐acetoxycubane‐1‐carboxylate (3), 1,4‐difluorocubane (4), 1,4‐dichlorocubane (5), and N,N‐diisopropylcubane‐1,4‐dicarboxamide (6) have been investigated by means of X‐ray diffraction analysis. Fluorine and chlorine substituents cause a shortening of the vicinal bonds, as is seen in the 4‐halocubane‐1‐carboxylates. The cage bonds vicinal to the ester substituent, with a favorable orientation with regard to the π‐acceptor influence of this group become longer than the CH–CH bonds. Furthermore, the influence on bond length with respect to the orientation of this group relative to bonds within the cubane skeleton has been investigated experimentally. The effect of the methoxy group has also been found to depend on the orientation. The cage bond antiperiplanar to the methyl group is shortened, while the cage bonds in gauche orientation to this group are lengthened. As seen in the case of the halogen‐substituted derivatives, the bonds bearing the acetoxy substituent are shortened due to the σ‐acceptor property of this group. Ab initio calculations on compounds 1, 2, 4, and 5 performed at the 6‐31G* level confirm the experimental results.

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The Cubane Cage – a Sensible Probe for Substituent Effects on a Four‐membered Ring

1996

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The crystals of methyl 4-fluoro-1-cubanecarboxylate ( l ) , methyl 4-chloro-1-cubanecarboxylate (2) and methyl cubanecarboxylate (5) are isomorphous to each other as are the crystals of methyl 4-bromo-1-cubanecarboxylate (3) and methyl 4-iodo-1-cubanecarboxylate (4). As a result of the space groups P2,/m and Pnma, respectively, all molecules lie in a crystallographic mirror plane. Therefore, the methoxycarbony1 group is exactly planar, and the carbonyl fragment is in an eclipsed position to the cubane skeletal bond C2-C7.The electronic effects of the halogen atoms, in particular fluorine and chlorine, give rise to a shortening of the vicinal skeletal bonds. In contrast, the methoxycarbonyl groups causes a lengthening of the vicinal skeletal bonds C2-C6 and C2-C6A which are not in an eclipsed conformation. Ab initio calculations at the 6-31G* level of compounds 1, 2, and 5 confirm the experimental results.The structure of three-membered rings is influenced by substituent effects ['] which are increased significantly in polycyclic systems with bridging They are sensible probes for these kinds of effects. For cyclobutane derivatives the substituent effects are already too weak to be detected unambigu~usly [~]. Therefore, we selected the cubane system which is composed of four-membered subunits within a strained polycyclic system. It should be suitable to detect substituent effects on four-membered ring bonds.Since Eaton and Cole presented the synthesis of cubaneL4I many chemists were engaged in cubane and its derivative~ [~]. This paper deals with the geometric alterations of the rigid cubane skeleton caused by several different substituents particularly by fluorine, because of its strong electronic effect [']. Since Fleischer investigated the crystal structureL61 of cubane itself, a large number of X-ray crystalstructure investigations of the different derivatives have been carried out, but to our knowledge no derivative bearing a fluorine atom on the cubane skeleton has previously been studied. In this paper we describe the crystal structures of the compounds 2-5 and of methyl 4-fluoro-1-cubanecarboxylate (1) in particular to demonstrate the geometric distortions of the cubane skeleton caused by the different substituent effect of the halogen atoms and the ester group. / MeOOC I H SynthesesStarting from 1,4-cubanedicarboxylic acid (6, Scheme 1) which was synthesized according to the method of Chapman et and in the case of the Favorskii rearrangement according to the method of Luh and we obtained the central half ester 8 by partial saponification of dimethyl 1,4-~ubanedicarboxylate (7)L91. The latter could be synthesized by methanolysis of the diacid dichloride of 6 in 85% yield. Methyl 4-iodo-and 4-fluoro-1 -cubanecarboxylate 4 and 1 were prepared as described by Della and Head [lo]. Methyl 4-bromo-1-cubanecarboxylate (3) was obtained by a Hunsdiecker decarboxylative bromination described by Della et al.["I. A decarboxylative chlorination in the Kochi reaction[l2I led to methyl 4-chloro-1-cubanecarboxylate (2). T...

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Dimethyl cubane-1,4-dicarboxylate

Cited by 3 publications

References 9 publications

Not Your Usual Bioisostere: Solid State Study of 3D Interactions in Cubanes

Not Your Usual Bioisostere: Solid State Study of 3D Interactions in Cubanes

The Cubane Cage – A Sensitive Probe for Assessing Substituent Effects on a Four-Membered Ring, Part II

The Cubane Cage – a Sensible Probe for Substituent Effects on a Four‐membered Ring

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