Reductive Dimerization of Macrocycles Activated by BBr₃

Abstract

A macrocyclic motif composed of carbazole and pyridine subunits linked by a carbonyl bridge (CO) forms a skeleton with a peripheral reactivity that leads to a pinacol-like coupling activated by BBr3, eventually entrapping a substantially elongated C–C bond. Slightly modified conditions lead to the efficient transformation of the CO unit to a CH2 linker that, after exposure to air, gives a dimeric molecule with multiple bonds between two macrocyclic units, as documented in spectroscopy and X-ray analysis.

B,N-doped PAHs from tridentate ‘Defects’ – a bottom-up convergent approach for π-extended systems

“…As observed, the carbonyl unit was efficiently reduced and bromide anion was attached to the carbon bridge, proving the potential of BBr 3 to act as a redox agent able to reduce the carbonyl unit. 22 The presence of bromine at the carbon bridge (for X-ray structure see Fig. 2) suggests an initial step consistent with a 1,2 addition of Br –BBr 2 to CO based on the acid–base interaction.…”

“…As anticipated, the presence of the triangular centre and carbonyl functionality (Scheme 1) led to different reactivity of both structural elements towards coordination 21 or C-C bond formation. 22 The initial reaction performed for 1a (Scheme 1, path a) resulted in the formation of system 2a as a single product. As observed, the carbonyl unit was efficiently reduced and bromide anion was attached to the carbon bridge, proving the potential of BBr 3 to act as a redox agent able to reduce the carbonyl unit.…”

“…2) suggests an initial step consistent with a 1,2 addition of Br-BBr 2 to CQO based on the acid-base interaction. This initial step leads to the removal of oxygen, followed by the reduction with Br À (2Br À -Br 2 + 2e) 22,23 and the protonation to eventually afford 2a that showed also lack of boron(III) coordination. The mono-pyridine systems 1b/1c were subjected to the same reductive conditions eventually observing lack of reactivity for 1c and recovery of the starting material, while 1b adopted the same path as 1a eventually afforded 2b.…”

Diagnosing Ring Current(s) in Figure-Eight Skeletons: A 3D Through-Space Conjugation in the Two-Loops Crossing

“…The synthetic approach (Scheme ) employs a transition-metal-catalyzed process documented as efficient in formation of macrocycles. , The incorporated subunits were chosen for being known for forming helical systems (carbazole) or being open for redox switching (furan) . The Suzuki–Miyaura coupling performed for 1 and commercially available 2 gave 3 with 67% yield.…”

Edge Decoration of Anthracene Switches Global Diatropic Current That Controls the Acene Reactivity

“…On the contrary, the geometric constraints introduced in specifically constructed motifs gave a field for testing the reactivity that was unavailable without a macrocycle . It could also force a close proximity of units in the cavity, resulting in, for example, strong hydrogen bonding . Thus the macrocyclic confinements present the potential for opening global conjugation, which can influence all involved subunits, including acenes, that, depending on the orientation, can serve as donors for a dopant entrapment and also introduce donors/acceptors for an unprecedented interaction.…”