Resorc[4]arenes 1 and 2, which previously proved to entrap NO+ cation within their cavities under conditions of host-to-guest excess, were treated with a 10-fold excess of NOBF4 salt in chloroform. Kinetic and spectral UV-visible analyses revealed the formation of isomeric 1:2 complexes as a direct evolution of the previously obsd. event. Accordingly, three-body 1-(NO+)2 and 2-(NO+)2 adducts were built by MM and fully optimized by DFT calcns. at the B3LYP/6-31G(d) level of theory. Notably, covalent nitration products 4, 5 and 6, 7 were obtained by reaction of NOBF4 salt with host 1 and 2, resp., involving macrocycle ring-opening and insertion of a nitro group in one of the four arom. rings. In particular, compds. 4 and 6, both contg. a trans-double bond in the place of the methine bridge, were oxidized to aldehydes 5 and 7, resp., after addn. of water to the reaction mixt. Calcn. of the charge and frontier orbitals of the arom. donor (HOMO) and the NO+ acceptor (LUMO) clearly suggests an ipso electrophilic attack by a first NO+ unit on the resorcinol ring, mediated by the second NO+ unit.
Reaction of Nitrosonium Cation with Resorc[4]arenes Activated by Supramolecular Control: Covalent Bond Formation / Ghirga, Francesca; D'Acquarica, Ilaria; Delle Monache, G.; Mannina, Luisa; Molinaro, Carmela; Nevola, Laura; Sobolev, A. P.; Pierini, Marco; Botta, Bruno. - In: JOURNAL OF ORGANIC CHEMISTRY. - ISSN 0022-3263. - STAMPA. - 78:(2013), pp. 6935-6946. [10.1021/jo400489m]
Reaction of Nitrosonium Cation with Resorc[4]arenes Activated by Supramolecular Control: Covalent Bond Formation
GHIRGA, FRANCESCA;D'ACQUARICA, Ilaria;MANNINA, LUISA;MOLINARO, CARMELA;NEVOLA, LAURA;PIERINI, MARCO;BOTTA, Bruno
2013
Abstract
Resorc[4]arenes 1 and 2, which previously proved to entrap NO+ cation within their cavities under conditions of host-to-guest excess, were treated with a 10-fold excess of NOBF4 salt in chloroform. Kinetic and spectral UV-visible analyses revealed the formation of isomeric 1:2 complexes as a direct evolution of the previously obsd. event. Accordingly, three-body 1-(NO+)2 and 2-(NO+)2 adducts were built by MM and fully optimized by DFT calcns. at the B3LYP/6-31G(d) level of theory. Notably, covalent nitration products 4, 5 and 6, 7 were obtained by reaction of NOBF4 salt with host 1 and 2, resp., involving macrocycle ring-opening and insertion of a nitro group in one of the four arom. rings. In particular, compds. 4 and 6, both contg. a trans-double bond in the place of the methine bridge, were oxidized to aldehydes 5 and 7, resp., after addn. of water to the reaction mixt. Calcn. of the charge and frontier orbitals of the arom. donor (HOMO) and the NO+ acceptor (LUMO) clearly suggests an ipso electrophilic attack by a first NO+ unit on the resorcinol ring, mediated by the second NO+ unit.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.