A highly selective synthesis of 1‐substituted (E)‐buta‐1,3‐dienes with 4,4,5,5‐tetramethyl‐2‐vinyl‐1,3,2‐dioxaborolane as building block

Abstract

Highly selective synthesis of 1‐substituted (E)‐buta‐1,3‐dienes via palladium‐catalyzed Suzuki–Miyaura cross‐coupling of (E)‐alkenyl iodides with 4,4,5,5‐tetramethyl‐2‐vinyl‐1,3,2‐dioxaborolane (1) is reported. The vinylboronate pinacol ester (1) acts as a vinyl building block to show high chemoselectivity for the Suzuki–Miyaura pathway versus Heck coupling in the presence of biphasic conditions (Pd(PPh3)4, aqueous K2CO3, toluene and ethanol). Copyright © 2014 John Wiley & Sons, Ltd.

A Diverted Aerobic Heck Reaction Enables Selective 1,3-Diene and 1,3,5-Triene Synthesis through C–C Bond Scission

“…Substituted 1,3-dienes are common synthetic building blocks featured in a wide array of complexity-building catalytic transformations, including recently developed asymmetric hydrofunctionalizations, difunctionalizations, C–H functionalizations, cycloadditions, and cross-coupling . Preparations of 1,3-dienes, 1-aryl-1,3-dienes being a particularly prevalent subset in modern catalytic methods, classically involve disconnections at the central σ bond of the diene, such as through Mizoroki–Heck reactions, cross-coupling, , and ene-yne metathesis, or disconnection at the double bond in the case of Wittig-type olefinations (Scheme , left) . Drawbacks of these approaches include functional group compatibility with strongly basic organometallic reagents or, more importantly, limited structural diversity in commercial starting materials (i.e., styrenyl halides or cinnamaldehydes).…”

“…The use of an industrially preferred solvent (2-MeTHF), molecular oxygen as the terminal oxidant, and the generation of benign byproducts (e.g., boric acid and water) are several attractive features of this method. Organoboron reagents also complement the substrates used in existing methods to prepare dienes and trienes, such as aldehydes , or haloarenes, while also avoiding the need for harsh oxidants or bases.…”

One-step preparation of novel 1-(N-indolyl)-1,3-butadienes by base-catalysed isomerization of alkynes as an access to 5-(N-indolyl)-naphthoquinones

“…There are previous syntheses of a 1-( N -carbazolyl)-1,3-butadiene and 1-( N -phtalimido)-1,3-butadiene, albeit by a completely different methodology, based on cross-coupling reactions of N -vinyl derivatives. 4 Since the obtained yield in the present work was higher than 90%, a family of these compounds was prepared in this way from different substituted indoles, and also from carbazole. The reaction was not feasible using K 2 CO 3 as base, either in acetone or DMSO, while the use of NaH or stronger bases would form alkyne salts.…”

“…Compared to the previous synthesis of 1-( N -indolyl)-carbazole in ref. 4 , the present methodology is simpler, and does not require the use of expensive organometallic catalysts or inert atmosphere.…”

“…4 , the present methodology is simpler, and does not require the use of expensive organometallic catalysts or inert atmosphere. Besides, this is a one-step process, a shorter route than the sequence of 2 or 3 steps in ref. 4 .…”