Azulenylcarbenes: Rearrangements on the C₁₁H₈ Potential Energy Surface

Abstract

Four isomeric azulenylcarbenes were synthesized in argon matrices by photolysis of the corresponding diazo precursors, and the photochemistry of these carbenes was studied. The carbenes and their rearranged products were characterized by IR, UV/Vis, and EPR spectroscopy, and the experimental data were compared to results from DFT calculations. While 2-, 5- and 6-azulenylcarbene show triplet ground states, 1-azulenylcarbene exhibits a singlet ground state, in accord with theoretical predictions. The rearrangements of the azulenylcarbenes give access to a number of unusual C11 H8 isomers, such as other carbenes and strained allenes.

Carbenes and Nitrenes: Recent Developments in Fundamental Chemistry

“…[28] Although this is far too high for the classical process in an Ar or aNematrix at 3-10 K, it will be very facile under FVP conditions,a nd this is described in Scheme 7. [29] Thef ormation of cyclopenta[cd]indene (33)i sr eadily explained in terms of the Sander rearrangement 27!28 and then ac ycloheptatetraene/phenylcarbene rearrangement 28!30!31.E lectrocyclization to 32 followed by a1 ,5-H shift generates 33.All these steps have very modest calculated barriers,which will be easily accessible under FVP conditions.…”

“…33 was also formed from 2‐azulenylcarbene 34 , thereby indicating the occurrence of a 2‐azulenylcarbene/1‐azulenylcarbene rearrangement by ring expansion/ring contraction . 1‐, 2‐, 5‐, and 6‐azulenylcarbenes have been characterized in matrix photochemistry …”

“…Similar to vinylnitrenes, vinylcarbenes have low D values (0.3–0.4 cm −1 ). The azulenylcarbenes have extraordinarily low D values on the order of 0.35 cm −1 , that is, much lower than the naphthylcarbenes (0.44–0.50 cm −1 ; Table S2). This can be taken as a statement of the fact that the aromaticity and resonance energy of azulene are much lower than for naphthalene, which means it is easier for azulene to give up some aromaticity and form an exocyclic double bond to the CH center.…”

Theoretical Investigation on C11H8 Bicyclic Carbene and Allene Isomers

“…Five azulenylcarbenes (1-, 2-, 4-, 5-, and 6-azulenylcarbene) are present in this group. Among them 1-azulenylcarbene (7R-5R-6), 2-azulenylcarbene (7R-5R-9), 5-azulenylcarbene (7R-5R-8), and 6-azulenylcarbene (7R-5R-18) have already been detected experimentally [71] except 4-azulenylcarbene (8R-5R-20). 8R-5R-6 had been isolated by Sander's group in 2012, through lowtemperature argon matrix in its singlet ground electronic state [64].…”

Polysubstituted Hexa-cata-hexabenzocoronenes: Syntheses, Characterization, and Their Potential as Semiconducting Materials in Transistor Applications

“…The cyclic π-conjugated organics composed of fused benzene moieties in different shapes and sizes have been considered as useful semiconducting materials in organic electronics, which owes its advancement to the availability of numerous aromatic compounds through the diligent efforts of synthetic chemists . Being the ubiquitous component of electronic devices, organic field-effect transistors (OFETs) based on organic semiconducting materials are particularly important .…”