title: Reaction of nitrosonium cation with resorc[4]arenes activated by supramolecular control: covalent bond formation.
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 observed event. Accordingly, three-body 1-(NO(+))2 and 2-(NO(+))2 adducts were built by MM and fully optimized by DFT calculations 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, respectively, involving macrocycle ring-opening and insertion of a nitro group in one of the four aromatic rings. In particular, compounds 4 and 6, both containing a trans-double bond in the place of the methine bridge, were oxidized to aldehydes 5 and 7, respectively, after addition of water to the reaction mixture. Calculation of the charge and frontier orbitals of the aromatic 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.
authors.affiliation: Dipartimento di Chimica e Tecnologie del Farmaco, Sapienza Università di Roma, P. le Aldo Moro 5, 00185 Roma, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Ghirga
authors.forename: Ilaria
authors.initials: I
authors.lastname: D'Acquarica
authors.forename: Giuliano
authors.initials: G
authors.lastname: Delle Monache
authors.forename: Luisa
authors.initials: L
authors.lastname: Mannina
authors.forename: Carmela
authors.initials: C
authors.lastname: Molinaro
authors.forename: Laura
authors.initials: L
authors.lastname: Nevola
authors.forename: Anatoly P
authors.initials: AP
authors.lastname: Sobolev
authors.forename: Marco
authors.initials: M
authors.lastname: Pierini
authors.forename: Bruno
authors.initials: B
authors.lastname: Botta
mesh_terms: D047250:Calixarenes / Q000737:chemistry*; D002412:Cations / Q000737:chemistry; D046911:Macromolecular Substances / Q000737:chemistry; D015394:Molecular Structure; D009569:Nitric Oxide / Q000737:chemistry*; D010649:Phenylalanine / Q000031:analogs & derivatives* / Q000737:chemistry; D011789:Quantum Theory
chemical_list: D002412:Cations; D046911:Macromolecular Substances; C504137:nitrosonium ion; C466160:resorcinarene; D047250:Calixarenes; D009569:Nitric Oxide; D010649:Phenylalanine