Facile Synthesis and Palladium‐Catalyzed Cross‐Coupling Reactions of 2,3‐Bis(pinacolatoboryl)‐1,3‐butadiene

Abstract

Treatment of 1,1-bis(pinacolatoboryl)ethene with an excess of 1-bromo-1-lithioethene gave 2,3-bis(pinacolatoboryl)-1,3-butadiene in high yield. Palladium-catalyzed cross-coupling of the resulting diborylbutadiene with aryl iodides took place smoothly in the presence of a catalytic amount of Pd(OAc)2/PPh3 and aqueous KOH to give 2,3-diaryl-1,3-butadienes in good yields. The coupling reaction with commercially available 4-acetoxyphenylmethyl chloride under the same conditions followed by hydrolysis of the acetyl groups gave anolignan B in a one-pot manner. A variety of [3]- to [6]dendralenes were synthesized by palladium-catalyzed coupling of the diene or 1,1-bis(pinacolato)borylethene with alkenyl or dienyl halides, respectively, in good yields.

Recent Advances in Boron‐Substituted 1,3‐Dienes Chemistry: Synthesis and Application

“…Cycloaddition reactions catalyzed by zinc and cobalt compounds are characterized by high regio‐ and diastereoselectivity and good enantioselectivity . In 2007, Carboni as well as Hiyama group applied 1,3‐dienylboronates in a sequence such as cycloizomerization/Diels–Alder/allylation catalyzed by palladium complexes, or cross‐metathesis/ring closing metathesis/Diels–Alder reaction catalyzed by ruthenium complexes (Scheme ; Path I and Path II) as an efficient method to generate tricyclic structures ( 273 or 275 ) with complete control of the stereogenic centers.…”

“…In 2007, Shimizu and co‐workers proved that the bis(pinacolatoboryl) diene 16 a could be used as a reagent with bis(pinacolato)diboron and aldehyde. The effect of this transformation is a triple aldehyde addition which gives 2,3‐bis(alkylidene)alkane‐1,5‐diols as products 411 (Scheme ) . The triple addition was reported for aryl as well as alkyl aldehydes.…”

Polyborylated reagents for modern organic synthesis

“…34) Diels-Alder reactions of 2 with electron-deficient alkenes and dimethyl acetylenedicarboxylate proceed smoothly upon heating, giving rise to the corresponding 1,2-diborylcyclohexenes and -1,4-cyclohexadiene that can serve as building blocks for polysubstituted cyclohexenes and benzenes, respectively, in conjunction with Pd-catalyzed cross-coupling reaction and oxidation using DDQ (Scheme 21). 35) …”

Synthesis of Stereodefined Borylated Dendralenes through Copper‐Catalyzed Allylboration of Alkynes

“…[8] Theh igh value of dendralenes and the growing interest in their chemistry calls for efficient synthetic methods.S of ar, procedures for the synthesis of dendralenes mainly rely on Niand Pd-catalyzed cross-coupling of alkenylmetal reagents with (bis)haloalkenes. [2,9] Aside from these transformations, other elegant catalytic alternatives include Rh-catalyzed C À H-activation, [10] Pd-and Rh-catalyzed coupling of allenyl derivatives [11,12] and Ru-catalyzed cascade reactions. [13] However,all of these synthetic methods require the pre-formation of the starting materials,t hus adding extra steps.M oreover, strategies that allow the synthesis of functionalized dendralenes are scarce and most of them require building blocks with preinstalled functional groups.I nv iew of this and the enormous synthetic potential of dendralenes,i ti sd esirable to develop catalytic methods that allow rapid access to functionalized dendralenes from simple and commercially available materials.F urthermore,i nstallation of av ersatile functional group such as ab oronic ester in the dendralenic structure would result in an organoboron compound of tremendous synthetic use since awide variety of dendralenes could be accessed through CÀBb ond functionalization [14] (dendralene to dendralene conversion), and synthesis of complex polycyclic structures bearing the boronic ester group could be accomplished by use of the unique dendralene reactivity.N otably,t ot he best of our knowledge,b orylated [3]dendralenes (and higher homologues) have never been reported.…”