Versatile Synthesis of Pentalene Derivatives via the Pd-Catalyzed Homocoupling of Haloenynes

Abstract

A palladium-catalyzed, reductive homocoupling of haloenynes yields a diverse range of polysubstituted pentalene derivatives, including annulated dibenzopentalenes and dithienylpentalenes.

Synthesis and Reactions of Dibenzo[a,e]pentalenes

“…Likewise, 29c reacted in PCD in the presence of a catalytic amount of tellurium to afford an 1:1 mixture of 1nn and 1oo in 83% yield. Two phenylacetylenes, one of which has a halogen atom and the other of which has a Bu 3 Sn group were coupled in the presence of CsF, t Bu 3 P and Pd 2 (dba) 3 to give dibenzopentalenes (Scheme 19) [41]. The coupling reaction of 30a and 31a under the reaction conditions shown in Scheme 19 provided dibenzopentalene 1a in 61% yield.…”

“…Heating of 31a and 31b afforded 1a and 1qq, respectively in very high yields with 2 equivalents of hydroquinone, Cs 2 CO 3 and CsF in the presence of catalytic amounts of t Bu 3 P and Pd 2 (dba) 3 in 1,4-dioxane at 135 ºC (Scheme 20) [41]. This method could be applied for the preparation of a variety of dibenzopentalenes (5572% yields) (Scheme 21) [41].…”

“…This method could be applied for the preparation of a variety of dibenzopentalenes (5572% yields) (Scheme 21) [41]. The most striking feature of this catalytic system is that a heteroaromatic analog 34 of a dibenzopentalene was able to be synthesized.…”

Dithieno[a,e]pentalene Based Conjugated Polymers: Synthesis and Characterization

“…[25][26][27] Some pentalene derivatives such as dibenzopentalenes have been perceived as useful building blocks for synthesis of conjugated polymers because of their rigid planar and conjugated structure. [28][29][30][31][32] Small molecules based on dibenzopentalenes have been synthesized and applied in organic electronic devices. [31] Substituted dithieno[a,e]pentalenes (DTPs) are stable compounds and the efficient synthetic methods for them have been developed lately.…”

π-Conjugated carbocycles and heterocycles via annulation through C-H and X-Y activation across CC triple bonds

“…Crossover annulation between 54 and 55 via C-Br/C-Sn cascade of two different alkynes gave good yields of dibenzopentalenes 56 having two different substituents at C-5 and C-10 positions. 111 However, it is highly desirable to synthesize such differently substituted dibenzopentalenes via crossover annulation, which proceeds efficiently through C-H bond activation, instead of C-Sn bond activation. Scheme 17.…”