13938-73-3Relevant academic research and scientific papers
A Novel Synthesis of 2,3-Dihydro-1,3-methano-1H-indene {(Bicyclo[2.1.1]hexeno)benzene} and Analysis of Its NMR Spectra
Christl, Manfred,Cohrs, Carsten
, p. 6315 - 6323 (2015)
A new synthesis of 2,3-dihydro-1,3-methano-1H-indene (3) has been designed with bicyclo[2.1.1]hex-2-ene serving as starting material, which was added onto chloro-substituted α-pyrones. The title hydrocarbon 3 was then obtained in two subsequent steps. The AA′MM′ 1H NMR spectrum of 3 was analyzed and simulated, leading to corrections of previously published coupling constants. The 13C NMR signal of the methylene carbon atoms appears at particularly low field (δ = 63.3 ppm). This finding is discussed together with anomalous low- and high-field absorptions of methylene carbon atoms of cyclobutanes and bridgehead carbon atoms of bicyclo[1.1.0]butanes, the 1,3- and 2,4-positions of which, respectively, are bridged by π electron systems. As a result, moieties with (4n + 2) π electrons cause deshieldings, whereas those having 4n π electrons evoke shieldings. The title compound was prepared from bicyclo[2.1.1]hex-2-ene, and its NMR spectra were analyzed in detail. Previously published 1H-1H coupling constants had to be revised. Surprisingly, the signal of the CH2 groups appear at considerably lower field in the 13C NMR spectrum than that of the benzylic carbon atoms.
