Synthesis, Chiroptical Properties, and Absolute Configuration of (+)-2,3-Dihydrotriquinacen-2-one. Effect of Rigid Triquinacene Geometry on the Inherently Dissymmetric Chromophore

Paquette, Leo A.; Farnham, William B.; Ley, Steven V.

doi:10.1021/ja00858a600

Cited by 23 publications

(7 citation statements)

References 11 publications

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“…The acid was resolved as its a-(+)-a-methylbenzylamine salt according to the procedure described previously. 7 Acidification of the head fraction after five recrystallizations gave white crystals: mp 112-113 °C;24 [a]25D -11.1°, [a]25365 -3 29°( c 0.24, C2H5OH); 92% ee.…”

Section: Methodsmentioning

confidence: 99%

“…^Derangement to (+)-2,3-dihydrotriquinacen-2-one whose absolute configuration was established as 15 (e.g., 4) on the basis of its chiroptical properties. 7 In the present study, a more expedient route to both 3 and 4 was devised (Scheme I).8 Treatment of 59 with hydrogen cyanide in a two-phase (ether-water) solvent system according to Ohkata10 was most effective in delivering the desired cyanohydrin. The action of phosphorus oxychloride in pyridine on 6 provided a mixture of triene nitrile 7 and endochloronitrile 8 in a 40:60 ratio.…”

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confidence: 95%

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The absorption and circular dichroism spectra of chiral triquinacenes

Paquette¹,

Kearney²,

Drake³

et al. 1981

J. Am. Chem. Soc.

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The three deuterated, optically active 2,3-dihydrotriquinacenes lla-c of known absolute configuration have been prepared from (+)-( 15)-2,3-dihydrotriquinacen-2-one (4). The optically active monodeuterated triquinacene 12 was obtained from the same precursor and (-)-(lS)-2-methyltriquinacene ( 15) from (-)-triquinacene-2-carboxylic acid. The chirality in 11 and 12 is due solely to isotopic substitution. Although the three dihydrotriquinacenes have CD effects smaller than could be measured, presumably because of the distance between the deuterium atoms and the chromophore, the absorption and circular dichroism spectra of 12 and 15 proved very revealing. The contributions of the composite double bonds and peripheral substituents to the observed Cotton effects are analyzed in a manner which is consistent with the observed transitions.The effect of deuterium as an isolated perturber on the electric dipole forbidden n -* * transitions of chiral deuterio ketones has recently been examined intensively and with considerable success.* 1 Simultaneously, there have appeared a smaller number of reports dealing with experimental assessment of the extent to which chiral isotopic perturbation is seen in the weaker electric dipole allowed -* ir* transitions of conformationally rigid olefins.2-4 The placement of a C-D bond at various positions in relatively inflexible ketones generates chiroptical contributions which are dissignate (antioctant). The same effect has been observed in (1S)-(1 -2 3H)apobornene (1) but not in 2 where the octant con-2 D tribution is consígnate.4 Such net contributions of deuterium substituents to the rotary strength have been attributed to shorter C-D bond lengths, effectively smaller size, and reduced polarizability relative to their C-H counterparts.4 Thus, a change in steric environment alone is presently considered capable of reversing the observed isotope-induced chiral perturbation.Because new and different chiral molecular systems can be expected to constitute interesting test cases for advanced models of chirality function, we were led to examine the absorption and CD spectra of optically active {\R,4SJR, 10S)-(2-2H)triquinacene,5 the related methyl derivative, and several 2,3-di-

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Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 95%

The absorption and circular dichroism spectra of chiral triquinacenes

Paquette¹,

Kearney²,

Drake³

et al. 1981

J. Am. Chem. Soc.

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“…1f and g) were synthesized relatively early on. 13 The spherical dodecahedrane eluded synthesis [14][15][16][17][18] until its total synthesis consisting of 29 steps was achieved. 19 Dodecahedrane (Fig.…”

Section: Cycloalkanes Containing Hexagons and Pentagonsmentioning

confidence: 99%

Dodecahedrane minibead polymers

Bánfalvi

2014

RSC Adv.

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“…(C2V, A, STO-2G)9 (C2U, 8-MR planar)46) clearly provides a good model for 9, as the STO-2G calculated bond lengths for these two ions correspond to within 0.002 Á (Figure5). A further comparison is provided by the tropenylium cation(11).11 (Dlh, A, …”

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confidence: 99%

Molecular orbital theory of homoaromatic character

Haddon¹

1979

J. Org. Chem.

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Ab initio STO-2G geometry optimizations have been carried out for the homotropenylium cation (1) and the cyclooctatrienylium cation [planar ( C, ) and nonplanar (C8)]. The homoconjugate W a g e for the homotropenylium cation is found to be 1.578 A at this theoretical level. This brings the ab initio calculations for 1 into line with previous MIND0/3 studies, frontier molecular orbital theories (FMOs), and the Winstein picture of an open cyclopropane unit in the homotropenylium cation. Both the homotropenylium cation and the cyclooctatrienylium cation are found to be markedly nonplanar when fully optimized. STO-BG, STO-3G, and 4-31G calculations on the STO-2G potential minima indicate that the cyclooctatrienylium cation probably lies no more than 10 kcal/mol higher in energy than the homotropenylium cation. This finding requires a revision of the concept of the homoaromatization energy for 1 and implicates the cyclooctatrienylium cation as an intermediate in the bridge-flipping process which occurs in the homotropenylium cation. MINDO/3 calculations are reported for the homotropenylium and cyclooctatrienylium cations together with results for other ions of interest in the area of homoaromatic chemistry. Evidence for homoaromatic character is found for the homotropenylium cation, the homocyclopropenylium cation, and the homocyclooctatetraene dication. The final frontier-dihomoaromatic character-is illustrated with the aid of calculations on the dihomotropenylium cation which is also found to be nonplanar. The homoaromatic cations show a number of well-defined trends. In particular it is shown that nonplanarity in the basal plane, shortened bond lengths between polyenyl and bridge fragments, bond equalization in the polyenyl segment, and lengthening of the homoconjugate linkage operate in concert to confer homoaromatic character. The bicyclo[5.2.0]nonadienylium cation, in which the cyclopropane group of the homotropenylium cation is replaced by a cyclobutane ring, does not exhibit the above characteristics and is concluded to be nonhomoaromatic. These results are in excellent agreement with previous FMO theories of homoaromatic character.The calculations for the homocyclopentadienyl anion and the .homocycloodatetraene dianion provide some evidence for homoaromatic character, but in contrast to the cations, the results for the anions do not lend themselves to a straightforward interpretation. The full sets of canonical molecular orbitals from the cyclooctatrienylium cation and the homotropenylium cation have been transformed to localized molecular orbitals (LMOs). The three *-type LMOs for the cyclooctatrienylium cation accord well with the notion of a heptatrienylium cation conjugation scheme. The *-type LMOs for 1 are of an entirely different character and most clearly evoke the conjugation of a cyclopropane unit with a pentadienyl cation in which each component has essentially retained its integrity. On this basis it is argued that the homotropenylium cation should be regarded as a resonance hybrid between the ful...

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Synthesis, Chiroptical Properties, and Absolute Configuration of (+)-2,3-Dihydrotriquinacen-2-one. Effect of Rigid Triquinacene Geometry on the Inherently Dissymmetric Chromophore

Cited by 23 publications

References 11 publications

The absorption and circular dichroism spectra of chiral triquinacenes

The absorption and circular dichroism spectra of chiral triquinacenes

Dodecahedrane minibead polymers

Molecular orbital theory of homoaromatic character

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