Chultack Lim

THE MENSCHUTKIN REACTION OF 1-ARYLETHYL BROMIDES WITH PYRIDINE: EVIDENCE FOR THE DUALITY OF CLEAN SN1 AND SN2 MECHANISMS

Abstract 1-Arylethyl bromides react with pyridine in acetonitrile by unimolecular and bimolecular processes. These processes are quite distinct and this fact affords clear evidence for the duality of clean S N 1 and S N 2 mechanisms, occurrence of independent S N 1 and S N 2 reaction processes without an intermediate mechanism.

Formation and structural features of novel cage compounds with a pentacyclo[6.4.0.03,7.04,11.05,10]dodecane skeleton via photolysis of [33](1,3,5)cyclophane

The photolysis of [3 3 ](1,3,5)cyclophane 8 in MeOH:2N HCl (17:1 v/v) afforded new polycyclic caged dimethoxy and methoxy–hydroxy compounds 12 and 13 with a novel pentacyclo[6.4.0.0 3,7 .0 4,11 .0 5,10 ]dodecane skeleton 7 , in addition to methyl ether 9c with the previously reported skeleton 6 . The unique structural features of 12 and 13 were elucidated by X-ray structural analysis.

Formation of novel cage compounds via photoreaction of [3.3.3](1,3,5)cyclophane

Abstract Photoirradiation of [3 3 ](1,3,5)cyclophane 11 with a low pressure Hg lamp in CH 2 Cl 2 in the presence or absence of water afforded new polycyclic cage compounds of chlorinated tribridged hexacyclododecane 12 or its hydroxy analogue 14 and tribridged tetracyclic olefin 13 .

Formation of a Novel Cage Compound with a Pentacyclo[6.3.0.14,11.02,6.05,10]dodecane Skeleton by Photolysis of [34](1,2,4,5)Cyclophane

Abnormally long C-C single bonds are found in the polycyclic caged diol with a pentacyclo[6.3.0.1(4,11).0(2,6).0(5,10)]dodecane skeleton formed by photolysis (see scheme). This skeleton resembles the structure of diamantane, but instead of having six cyclohexane rings in a chair conformation it contains only two cyclohexane rings in a distorted chair conformation and four cyclopentane rings, which makes it more highly strained than diamantane.

Photolysis of [34](1,2,3,5)cyclophane: formation of a pentacyclo[6.3.1.16,10.03,7.04,10]dodecane skeleton with abnormally elongated CC single bonds

Abstract The photolysis of [34](1,2,3,5)cyclophane 5 in H2O-saturated CH2Cl2 produced the novel polycyclic caged diol 6 with a pentacyclo[6.3.1.16,10.03,7.04,10]dodecane skeleton 4, which has abnormally elongated CC single bonds (1.624 A). The structural features of 6 were studied using the X-ray structural analysis and ab initio MO calculations.

Improved Synthesis, Structure, and Cycloaddition Reaction of [34](1,2,4,5)Cyclophane

The modified synthetic route to [34](1,2,4,5)cyclophane (3) provides gram quantities of this compound in fewer steps than the conventional routes. The cycloaddition of 3 with dicyanoacetylene (12) gave barrelenophane 13, which was transformed into semibullvalenophane 15 on photoirradiation. This transformation (13 15) is in sharp contrast to the case of Boekelheides [24]barrelenophane, where cyclooctatetraenophane is obtained. The X-ray structural analyses of 3, 13, and 15 demonstrates their unique structures.

The Menschutkin reaction of benzyl p‐toluenesulfonates with N,N‐dimethylanilines. Evidence for the duality of SN1 and SN2 mechanisms

The rate data for the Menschutkin reaction between strongly activated Z-substituted benzyl p-toluenesulfonates and Y-substituted N,N-dimethylanilines in acetonitrile at 35 °C fit the equation, kobs  =  k1 + k2 [DMA], which is consistent with concurrent first- and second-order processes. The k1 and k2 values for each substrate were separated based on the above equation. The SN1 rate constant, k1, is unaffected by the nature of the nucleophile, whereas the SN2 rate constant, k2, increased with the electron-donating substituent of the N,N-dimethylaniline. The substituent effect on the k1 values is linearly correlated by the Yukawa–Tsuno equation with ρ  =  −5.2 and r  =  1.3. The unimolecular reaction can be regarded as a classical SN1 mechanism. In contrast, that on the k2 values shows an upward curvature when analyzed by the Brown σ+ treatment. These results are ascribed to the simultaneous and independent occurrence of SN1 and SN2 mechanisms in the present Menschutkin reaction.

Bildung einer neuartigen Käfigverbindung mit einem Pentacyclo[6.3.0.14,11.02,6.05,10]dodecan‐Skelett durch Photolyse von [34](1,2,4,5)Cyclophan

Ungewohnlich lange C-C-Einfachbindungen liegen in dem photochemisch erhaltenen polycyclischen Kafigdiol vor, das ein Pentacyclo[6.3.0.14,11.02,6.05,10]dodecan-Skelett enthalt (siehe Schema). Dieses Gerust ahnelt dem von Diamantan, enthalt aber im Unterschied zu diesem nicht sechs Cyclohexanringe in Sesselkonformation, sondern zwei Cyclohexanringe in einer verzerrten Sesselkonformation und vier Cyclopentanringe, weshalb es wesentlich starker gespannt ist als Diamantan.