Exploring the Reactivity of α-Lithiated Aryl Benzyl Ethers: Inhibition of the [1,2]-Wittig Rearrangement and the Mechanistic Proposal Revisited.
By carefully controlling the reaction temperature, treatment of aryl benzyl ethers with tBuLi selectively leads to α-lithiation, generating stable organolithiums that can be directly trapped with a variety of selected electrophiles, before they can undergo the expected [1,2]-Wittig rearrangement. This rearrangement has been deeply studied, both experimentally and computationally, with aryl α-lithiated benzyl ethers bearing different substituents at the aryl ring. The obtained results support the competence of a concerted anionic intramolecular addition/elimination sequence and a radical dissociation/recombination sequence for explaining the tendency of migration for aryl groups. The more favored rearrangements are found for substrates with electron-poor aryl groups that favor the anionic pathway.
Área de Química Orgánica, Departamento de Química, Facultad de Ciencias, Universidad de Burgos, Pza. Misael Bañuelos s/n, 09001, Burgos, Spain.
Rocío
R
Velasco
Departamento de Química Orgánica, Universidade de Vigo, Campus As Lagoas, 32004-, Ourense, Galicia, Spain.
Carlos
C
Silva López
Departamento de Química Orgánica, Universidade de Vigo, Campus As Lagoas, 32004-, Ourense, Galicia, Spain. faza@uvigo.es.
Olalla
O
Nieto Faza
Área de Química Orgánica, Departamento de Química, Facultad de Ciencias, Universidad de Burgos, Pza. Misael Bañuelos s/n, 09001, Burgos, Spain. rsd@ubu.es.
Roberto
http://orcid.org/0000-0003-2830-0892
R
Sanz
Wittig rearrangement; density functional calculations; lithiation; oxygen heterocycles; reaction mechanisms