[4+3] versus [4+2] Mechanisms in the Dimerization of 2-Boryl-1,3-butadienes. A Theoretical and Experimental Study
摘要:
The thermal dimerization of 2-boryl-1,3-butadienes and the scope of this reaction to prepare sixmembered rings difficult to synthesize by other methodologies have been studied. In addition, the nature of this dimerization has been studied theoretically. It has been found that the reaction coordinate associated with the formation of the cycloadduct of lowest energy has significant [4+3] character. This behavior is caused by the favorable carbon-carbon overlap and the large values of the corresponding resonance integrals. However, beyond the transition structure, the [4+2] pathway becomes the preferred one thus leading to the exclusive formation of the [4+2] cycloadduct. Aside from this effect, donating groups at the boryl moiety favor the [4+2] mechanism.
[EN] AZABICYCLO (3.1.0) HEXANE DERIVATIVES USEFUL AS MODULATORS OF DOPAMINE D3 RECEPTORS [FR] DERIVES AZABICYCLO (3.1.0) HEXANE UTILES COMME MODULATEURS DES RECEPTEURS D3 DE LA DOPAMINE
A simple preparation of N-substituted 3-pyrroline boromic esters from primary amines is described. The Suzuki-Miyaura coupling of these heterocycles with aryl halides proceeds in good yields. Alternatively, oxidation withDDQ or MnO 2 gives the corresponding pyrroles, which can be also engaged in subsequent palladium cross-coupling reactions.