Direct Cross‐Couplings of Propargylic Diols

Abstract

[Pd(PPh3 )4 ] catalyzes a Suzuki-Miyaura-like twofold cross-coupling sequence between underivatized propargylic diols and either aryl or alkenyl boronic acids to furnish highly substituted 1,3-dienes. Thus, 2,3-diaryl-1,3-butadienes and their dialkenic congeners ([4]dendralenes) are delivered in a (pseudo)halogen-free, single-step synthesis which supersedes existing methods. Allenols are also readily formed. Treatment of these single- and twofold cross-coupled products with acid leads to remarkably short syntheses of highly-substituted benzofulvenes and aryl indenes, respectively.

Synthesis and Properties of 2,3‐Diethynyl‐1,3‐Butadienes

“…We recently reported [19] that tetrasubstituted 2-butyne-1,4-diols (5,R 1 -R 4 ¼ 6 H) undergo twofold Pd 0 -catalyzed couplings with aryl (and some alkenyl) boronic acids,without the need to pre-activate the hydroxyl functionality [20] through covalent derivatization, to form densely substituted 1,3butadienes.T he twofold cross-coupling proceeds with 1,3transposition at each (C À Ot oC À C) bond change (see 2! [8]!4 in Scheme 2).…”

“…As mentioned in the Introduction, the Hopf laboratory reported the [4+ +4]-cyclodimerization of DEBD 11 h in 34 %yield from an initial 1.0 m concentration solution with no sign of the [4+ +2]-cyclodimer. [10b] In our hands,heating concentrated solutions of DEBDs 11 j and 11 h led to substantial polymerization and low yields of dimers,b oth in the presence and absence of acid scavengers as well as radical traps.M oreover,w eo bserved the formation of a % 2:3 mixture of the [4+ +2]-cyclodimer (18,19)a nd the [4+ +4]cyclodimer (16,17)i nb oth cases (Scheme 4).…”

Transition-Metal-Catalyzed Suzuki–Miyaura-Type Cross-Coupling Reactions of π-Activated Alcohols

“…Propargylic diols were utilized by Sherburn and coworkers in 2016 in the Suzuki-Miyaura-type cross-coupling reaction (Scheme 24). 39 Both twofold cross-coupled product, symmetrical 2,3-diaryl-1,3-dienes 155, and allenic alcohols 156 were obtained in moderate to excellent yields. The yield of allenic alcohols increased when increasing the steric bulk of the alcohols and arylboronic acids.…”

Ene-yne Cross-Metathesis for the Preparation of 2,3-Diaryl-1,3-dienes

“…2-Aryl-and 2,3-diaryl-dienes of type A have been extensively studied for the access to cyclic products resulting from Diels-Alder [4,22] They have also been recently involved in iridium-catalyzed hydrohydroxymethylation [25] and ruthenium-catalyzed hydroxymethylation [26]. Elimination reactions such as the thermal decomposition of 3,4-diaryldihydrothiophene-1, 1-dioxides [27] and the acid-catalyzed dehydration of 1,2-diol derivatives [28] have been used for the synthesis of 2,3-diaryl-buta-1,3-dienes of type A. But-2-yn-1,4-diol biscarbonates have been efficiently coupled with aryl and heteroaryl boronic acids in the presence of a palladium catalyst to give 2,3-diarylated 1,3-dienes [1, 29,30]. 1,4-Dimethoxybut-2-yne was also found to be an excellent substrate for the copper(I)-catalyzed SN2'substitution with aryl Grignard reagents to produce symmetrical 2,3-diarylbuta-1,3-dienes [31].…”

“…Using ethylene as olefinic substrate allows the production of buta-1,3-dienes with two terminal methylene groups according to a catalytic cycle initially proposed by M. Mori [46] and further studied in more details by S. T. Diver [47,48]. However, if many examples involving ruthenium-catalysis have been described starting from aliphatic including benzylic and propargylic alkynes [49][50][51][52], much less data are available from aromatic alkynes in the Elimination reactions such as the thermal decomposition of 3,4-diaryldihydrothiophene-1,1-dioxides [27] and the acid-catalyzed dehydration of 1,2-diol derivatives [28] have been used for the synthesis of 2,3-diaryl-buta-1,3-dienes of type A. But-2-yn-1,4-diol biscarbonates have been efficiently coupled with aryl and heteroaryl boronic acids in the presence of a palladium catalyst to give 2,3-diarylated 1,3-dienes [1, 29,30]. 1,4-Dimethoxybut-2-yne was also found to be an excellent substrate for the copper(I)-catalyzed SN2'substitution with aryl Grignard reagents to produce symmetrical 2,3-diarylbuta-1,3-dienes [31].…”