The Synthesis of Dibenzo-Annelated Annulenes Using Reductive Coupling. Bisdehydrodibenzo[14]-, -[16]-, -[18]-, -[20]-, and -[22]annulene

Abstract

Bisdehydrodibenzo[14]-, -[16]-, -[18]-, -[20]-, and -[22]annulene were synthesized by intramolecular reductive couplings using a low-valent titanium reagent. These bisdehydrodibenzo-annulenes proved to be atropic from an examination of the 1H NMR spectra.

Carbonyl-coupling reactions using low-valent titanium

“…Thus far, the keto ester coupling reaction has been used in syntheses of capnellene (88)123 and isocaryophyllene (91). 124 The capnellene synthesis used the reaction to form a cyclopentanone ring, and the isocaryophyllene synthesis formed a cyclononenone ring.…”

The McMurry Coupling and Related Reactions

“…The ability of the McMurry reaction to form medium-and large-sized rings efficiently, while at the same time building in considerable strain is also evident in the synthesis of the betweenanene 75 [101] and the heptafulvalene 76; the latter results from a transannular carbonyl coupling reaction and was transformed into displeiadiene after dehydrogenation [102]. A variety of conjugated cyclic polyenes, such as 77 and 78 [103,104], as well as unique examples of cyclo-1,3-dien-5-ynes 79 [105], have been prepared by the intramolecular coupling of dialdehydes. The tetraene 80, which was investigated as a tetradentate ligand for transition metals, accommodates an Ag þ ion within the cavity to give a unique square-planar com- plex [106].…”

Enantioselective Sensing of Amines Based on [1 + 1]-, [2 + 2]-, and [1 + 2]-Condensation with Fluxional Arylacetylene-Derived Dialdehydes

“…Dialdehyde 2 was readily available through oxidative homocoupling of 2-ethynylbenzaldehyde as described in the literature (Scheme 1). 18 The elongated analogue 3 was prepared by Sonogashira coupling of 2-bromobenzaldehyde and 1,4-diethynylbenzene in 80% yield. Slow evaporation of a solution of 2 in dichloromethane gave single crystals suitable for X-ray diffraction.…”