Multicomponent Synthesis of 6<i>H</i>-Dibenzo[<i>b,d</i>]pyran-6-ones and a Total Synthesis of Cannabinol

A multicomponent domino reaction that affords 6<i>H</i>-dibenzo[<i>b,d</i>]pyran-6-ones is reported. The overall transformation consists of six reactions: Knoevenagel condensation, transesterification, enamine formation, an inverse electron demand Diels–Alder (IEDDA) reaction, 1,2-elimination, and transfer hydrogenation. Both the diene and dienophile for the key inverse electron demand Diels–Alder (IEDDA) step are generated <i>in situ</i> by secondary amine-mediated processes. In most cases, the yields (10–79%) are considerably better than those obtained using a stepwise process. This methodology is employed in a concise total synthesis of cannabinol

A Macrocyclization of 1,8-Bis(dithiafulvenyl)pyrenes

Dithiafulvenyl (DTF) end groups were linked to the 1 and 8 positions of a pyrene core directly or via phenylene bridges to afford redox-active pyrene derivatives. Upon oxidation, the 1,8-bis­(DTF)­pyrene underwent stepwise electron transfers to form radical cation and dication species, whereas the phenylene-extended bis­(DTF)­pyrene derivative was cyclized into a macrocyclic trimer through sequential DTF oxidative coupling reactions in solution and in the solid state. The structural, electronic, and supramolecular properties of the pyrene-based macrocycle were investigated using various spectroscopic techniques and molecular modeling studies

Synthesis, Crystal Structure, and Resolution of [10](1,6)Pyrenophane: An Inherently Chiral [<i>n</i>]Cyclophane

A synthetic approach to a set of three inherently chiral [<i>n</i>]­cyclophanes, [<i>n</i>]­(1,6)­pyrenophanes (<b>29a</b>–<b>c</b>, <i>n</i> = 8–10) was investigated. Progress toward <b>29a</b> was thwarted by the failure of the key dithiacyclophane-forming reaction. For the next higher homologue, the synthesis was completed, but the desired [9]­(1,6)­pyrenophane (<b>29b</b>) could only be partially separated from an isomeric pyrenophane, [9]­(1,8)­pyrenophane (<b>28b</b>), and an unidentified byproduct. Work aimed at the synthesis of the next higher homologue resulted in the isolation of a 7:4 mixture of [10]­(1,8)­pyrenophane (<b>28c</b>) and [10]­(1,6)­pyrenophane (<b>29c</b>), which could not be separated by column chromatography or crystallization. However, single-crystal X-ray structures of <b>28c</b> and <b>29c</b> were obtained after manual separation of two crystals with different morphologies from the same batch of crystals obtained from the 7:4 mixture of <b>28c</b> and <b>29c</b>. The pyrene system of <b>29c</b> was found to have a gentle end-to-end bend as well as a significant longitudinal twist. Short intermolecular C­(sp³)–H···π contacts (2.64 to 2.76 Å) between H-atoms on the bridge and the centroids of three of the four six-membered rings of the pyrene system of a neighboring pyrenophane of like chirality give rise to the formation of single enantiomer columns. From a DNMR study of the mixture of <b>28c</b> and <b>29c</b>, the bridge in [10]­(1,8)­pyrenophane (<b>28c</b>) was found to undergo a conformational flip from one side of the pyrene system to the other with Δ<i><i>G</i></i>^⧧ = 14.9 ± 0.2 kcal/mol. A two-stage preparative HPLC protocol was subsequently developed for the separation of <b>28c</b> and <b>29c</b> (Chiralpak AD-H column) and then the enantiomers of <b>29c</b> (Chiralcel OJ-H column). This enabled the measurement of their optical rotations and CD spectra

A C‑Pyrenyl Poly(methylenephosphine): Oxidation “Turns On” Blue Photoluminescence in Solution and the Solid State

A C-pyrenyl poly­(methylenephosphine) (<i>M</i>_n = 4800, <i>Đ</i> = 1.56) was synthesized from the anionic polymerization of a P-mesityl phosphaalkene. The phosphine oxide polymer exhibits blue fluorescence in solution (λ_max 379, 400 nm, λ_onset 560 nm; Φ = 0.05) and blue-green fluorescence in the solid state at room temperature (λ_max 460 nm, Φ = 0.07). In contrast, unoxidized polymer displays only a weak emission in solution and no emission in the solid state. Fluorescence studies of partially oxidized polymers (50, 75, 83% oxidation) indicate that “turn on” emission occurs only at very high degrees of oxidation (near 100%). We conclude that even a small number of unoxidized phosphine moieties within the partially oxidized polymer intramolecularly quench the fluorescence