The Dienyl Pauson–Khand Reaction

Abstract

Studies in our organometallic subgroup are aimed at the design and development of new catalytic reactions, with an emphasis on processes that, in the absence of catalysts, would be forbidden or would require harsh conditions. [1,2] These studies have thus far produced the first examples of transition-metal-catalyzed [4þ4] cycloadditions of bisdienes, [3] [4þ2] cycloadditions of dienynes (and diene allenes), [4] [5þ2] cycloadditions of vinylcyclopropanes and p systems, [5] and [6þ2] cycloadditions of vinylcyclobutanones and p systems.[6] Recently, we started to investigate whether these and other two-component [mþn] cycloadditions could be converted into multicomponent [mþnþo…þx)] processes through trapping of the organometallic intermediates with additional components. [7] These investigations have thus far led to the first metal-catalyzed, three-component [5þ2þ1] cycloaddition reactions based on trapping of an intermediate in the [5þ2] cycloaddition reaction with CO.[8] The current study was directed at determining whether intermediates in the [4þ2] cycloaddition of dienynes could be similarly trapped with CO.Outlined in Scheme 1 are three competing metal-catalyzed cycloaddition pathways available for a dienyne in the

The Allenic Pauson−Khand Reaction in Synthesis

“…In view of the potential synthetic utility of this dienic version, Wender and co-workers focused their attention on the selectivity of the reaction of dienynes for the intramolecular [2ϩ2ϩ1] pathway. [30] Internal alkynes gave excellent yields of the PK cycloadducts (85Ϫ96% yield), whereas terminal alkynes reacted less efficiently. Substitution at the 2-or 3-position of the diene was also tolerated well.…”

Toward the ideal synthesis and transformative therapies: the roles of step economy and function oriented synthesis

“…When this idea of extending the [4+2] process to a three-component process was tested, all three modes ([4+2], [2+2+1], and [4+2+1]) of reaction were observed (Scheme 25). 71, 72 The [2+2+1] process was selected for optimization, providing the first examples of intra- and intermolecular dienyl Pauson-Khand reactions (Scheme 26). 71, 73 This concept of “sustaining reactivity” or “regenerating reactivity” laid out by us in the form of “connectivity analysis” in 1993, is a core principle in multicomponent reaction design.…”

“…71, 72 The [2+2+1] process was selected for optimization, providing the first examples of intra- and intermolecular dienyl Pauson-Khand reactions (Scheme 26). 71, 73 This concept of “sustaining reactivity” or “regenerating reactivity” laid out by us in the form of “connectivity analysis” in 1993, is a core principle in multicomponent reaction design. 3a,74 Collectively, such reactivity sustaining cascades are amongst the most powerful ways of building complexity, and thus value, with step economy.…”

Rhodium(iii)-catalyzed oxidative carbonylation of benzamides with carbon monoxide

“…1 Carbon monoxide as a C1 feed stock has been employed in a variety of palladium catalyzed transformations, 2,3 including the formation of esters from aryl halides, 4 aryl tosylates, 5 alkyl and aryl indium reagents among many others. 6 Furthermore, cyclopentanones have been formed via the Pauson-Khand reaction between an alkene, alkyne and CO. 7 In these cases the organometallic intermediate inserts CO as a π-component to access molecules with increased complexity.…”