Relationship between reactivity and 13C chemical shifts of benzocyclobutenes

Biological and structural properties’ interpretation on antitumour drug 3-(2-aminoethyl) indole (tryptamine) using molecular spectroscopy and computational tools

“…The observed data from 13 C and 1 H NMR spectra were used for estimating the chemical environment of chemical compound and also for validating the chemical potential rate of the molecular entities in the large number of chemical and biochemical systems. The nodal point of core atoms can be identified through which the reaction rate mechanism takes place in various locations for resulting drug activities [37]. The chemical potential energy generated in the molecular compositional parts for producing desired chemical property can be decoded by observing Chemical Shift.…”

A new synthesis of benzocyclobutenes. Thermal and electron impact induced decomposition of 3-isochromanones

“…Although the sequence 1 -* 2 -*• 3 was recognized early in the development of benzocyclobutene chemistry,3 it was not used synthetically until 1971 in the original synthesis of chelidonine (4 -*• 5 -* 6).9 Recent syntheses of berberines,10 spirobenzylisoquinolines,113-arylisoquinolines,12 benzocarbazoles,13 yohimbanes,14 and tetracy-clines15 have also utilized the Diels-Alder reactivity of dienes (2) derived by the thermolysis of benzocyclobutenes (l). 16 Because of their synthetic potential, intramolecular cyclizations similar to that used in the chelidonine synthesis have been examined in more detail,17 the mechanisms of intermolecular cyclizations have been discussed,18 the ease of electrocyclic ring openings of benzocyclobutenes have been correlated with their 13C NMR chemical shifts, 19 and the Diels-Alder reactions of the o -quinodimethane (24a) generated by ring opening of 4-methoxybenzocyclobutene (25a) have been considered in terms of frontier orbital theory. 20 Simultaneous with the development of new synthetic methods using benzocyclobutenes as intermediates has been the appearance of a host of new syntheses of benzocyclobutene and its derivatives.…”

“…An optimal 85% yield of pure benzocyclobutene was obtained at pyrolysis temperatures of 565-575 °C. 3-Isochromanone (20) was prepared in 70-80% yield by the Baeyer-Villiger oxidation of 2-indanone (19). 30 Thus this two-step sequence provides a simple and efficient synthesis of benzocyclobutene (21) from commercially available 2-21 indanone (19)31 in an overall yield of 60-65%.…”

Competitive reactions between sigmatropic reaction and cycloaddition affected by geometry of o-quinodimethanes

“…The intermolecular cycloaddition of o-quinodimethanes has been considered in terms of frontier orbital theory22 and ease of electrocyclic ring opening of benzocyclobutenes has been related to their 13C NMR chemical shifts. 23 As benzocyclobutenes used in the above reactions have one substituent on the cyclobutene ring, o-quinodimethanes generated from 1 by conrotatory ring opening18 could take an E form (2) which is thermodynamically more stable, but not a Z form (3).9•13 Therefore, we are interested in the geometry of o-quinodimethanes formed from benzocyclobutenes having geminal substituents on a cyclobutene ring, and here we wish to report the structure of o-quinodimethanes and also the [l,5]-sigmatropic reaction of the o-quinodimethane system, the latter of which is a new reaction1•24 of benzocyclobutenes.…”

“…Heating the 1,1-dialkylated benzocyclobutene 18 in dry toluene at 250 °C for 72 h in a sealed tube gave a separable mixture of (E)- (22) [ymax (CHCI3) 2230 cm-1; (CCLJ 2.16 (3 H, s, ArMe)] and (Z)-styrenes (23) [ymax (CHC13) 2230 cm-1; (CCI4) 2.19 (3 H, s, ArMe)] in a ratio of 3:2. The structure of both products was determined spectroscopically.…”