Terminal Alkyne Activation by Frustrated and Classical Lewis Acid/Phosphine Pairs

Dureen, Meghan A.; Stephan, Douglas W.

doi:10.1021/ja903650w

Cited by 420 publications

(251 citation statements)

References 38 publications

Supporting

Mentioning

237

Contrasting

Unclassified

Order By: Relevance

“…The first example of an aluminum-based Lewis acid in FLP chemistry was reported in 2009; the strong Lewis acid Al(C 6 F 5 ) 3 , in combination with P t Bu 3 or P(o-tol) 3 , was found to activate the terminal alkyne phenylacetylene, leading to either the deprotonation of the alkyne or the zwitterionic 1,2-addition product (Scheme 7). 43 In both cases, analogous reactivity was previously observed for B(C 6 F 5 ) 3 . Similarly, the FLP Al(C 6 F 5 ) 3 /P t Bu 3 reacts with ethylene generating the 1,2-addition product, whereas reaction with isobutylene results in CH bond activation to afford a phosphonium bis-Al allyl salt (Scheme 7).…”

Section: Overview Of Frustrated Lewis Pairssupporting

confidence: 75%

Main Group Lewis Acids in Frustrated Lewis Pair Chemistry: Beyond Electrophilic Boranes

Weicker

Stephan

2015

Bulletin of the Chemical Society of Japan

Self Cite

117

View full text Add to dashboard Cite

The advent of frustrated Lewis pair (FLP) chemistry almost a decade ago was based on the reactivity of sterically encumbered combinations of electrophilic boranes and phosphines with hydrogen. Since that time the chemistry has broadened dramatically in terms of reactivity and applications. Nonetheless, the majority of the work has continued to exploit the borane B(C6F5)3. In this review, we describe FLP chemistry that has developed by employing alternatives to this Lewis acid. Lewis acids derived from group 13, 14, and 15 based systems are described, thus demonstrating a growing area in the main group reactivity based on FLPs.

show abstract

Section: Overview Of Frustrated Lewis Pairssupporting

confidence: 75%

Main Group Lewis Acids in Frustrated Lewis Pair Chemistry: Beyond Electrophilic Boranes

Weicker

Stephan

2015

Bulletin of the Chemical Society of Japan

Self Cite

117

View full text Add to dashboard Cite

show abstract

“…It is known from previous publications that FLPs react with terminal alkynes via deprotonative borylation pathway, producing the respective onium alkynylborates 41,42,43,44,45,46 . Indeed, 6 reacts with hex-1-yne giving the respective adduct 31 (Scheme 6).…”

Section: Alkenes Under Hydrogenation Conditionsmentioning

confidence: 99%

A frustrated-Lewis-pair approach to catalytic reduction of alkynes to cis-alkenes

et al. 2013

View full text Add to dashboard Cite

Recently, a new approach to dihydrogen activation known as frustrated Lewis pairs (FLPs) concept has been introduced 1, 2, 3 . A combination of highly Lewis acidic boranes and sterically hindered bases can split hydrogen heterolytically generating onium (phosphonium, ammonium, etc.) borohydrides. These compounds show reduction activity resembling that of inorganic borohydrides like NaBH 4 , i. e. they are suitable mostly for reduction of polarized multiple bonds. Imines, enamines, silyl ethers 4, 5,6 , α,β-enones 7 , ynones 8 , Nalkylanilines 9 were hydrogenated using stoichiometric or catalytic amounts of FLPs. Due to heterolytic nature of FLP-H 2 adducts, hydrogenation of unactivated multiple C-C bonds using FLPs has some natural limitations, since during the respective step of the catalytic cycle a proton transfer from catalyst to substrate should take place (Fig. 1a). Although Greb et al. have implemented this approach to hydrogenation of alkenes under ambient conditions, this method is predictably restricted to the alkenes with high proton affinity 10 .

show abstract

“…The same group also showed that some alkenes could undergo C-H bond cleavage using the combination of aluminum compounds and Lewis bases [91]. Terminal alkynes can also be activated by suitable FLPs in a process that is somewhat reminiscent of the copper-assisted deprotonation of alkynes that is at the core of the Sonogashira cross-coupling [25,[92][93]. However, none of these C-H bond cleavage processes could be used for catalytic transformations.…”

Section: C-h Borylation Of Heteroarenes: a Proof Of Conceptmentioning

confidence: 99%

Design principles in frustrated Lewis pair catalysis for the functionalization of carbon dioxide and heterocycles

Fontaine

Courtemanche

Légaré

et al. 2017

Coordination Chemistry Reviews

102

View full text Add to dashboard Cite

This is the peer reviewed version of the following article: [Design Principles in Frustrated Lewis KeywordsFrustrated Lewis pairs, Ambiphilic molecules, Boron, Aluminum, Carbon dioxide, Methanol, C-H activation. Highlights 1.Phosphine-aluminum frustrated Lewis pairs (FLPs) can activate CO2 but show significant stability issues. 2.The Lewis acidity and basicity need to be fine-tuned to the desired reactivity for efficient FLP catalysis.3. FLP catalysts need to generate strong hydrides to reduce catalytically carbon dioxide. 4.Transition metal catalysis can serve as an inspiration for the design of metal-free catalysts for many transformations, including the borylation of heteroarenes. Graphical abstract AbstractThis account describes our work on the use of ambiphilic molecules as catalysts for the reduction of carbon dioxide. Starting with the discovery that aluminum ambiphilic species (Me2PCH2AlMe2)2 (1) and Al(C6H4-PPh3)3 (5) could coordinate CO2 but showed significant instability, we found that phosphinoborane Ph2P-2-Bcat-C6H4 (7) was an exceptional catalyst for the hydroboration of CO2 to methoxyboranes, a molecule that can be readily hydrolyzed to methanol. A mechanistic investigation allowed us to outline the similarities between the catalytic activity of frustrated Lewis pairs (FLPs) and that of transition metal complexes. We were able to extrapolate four important guidelines, described in this account, to synthesize efficient metal-free catalysts. We demonstrate that using these concepts it was possible to rationally design FLP catalysts for the C-H borylation of heteroarenes.

show abstract

Terminal Alkyne Activation by Frustrated and Classical Lewis Acid/Phosphine Pairs

Abstract: Frustrated and classical Lewis pairs arising from combinations of Lewis acids and phosphines react with terminal alkynes either via C-H activation forming an alkynylborate salt or by addition to alkyne giving a zwitterionic phosphonium borate.

Cited by 420 publications

References 38 publications

Main Group Lewis Acids in Frustrated Lewis Pair Chemistry: Beyond Electrophilic Boranes

Main Group Lewis Acids in Frustrated Lewis Pair Chemistry: Beyond Electrophilic Boranes

A frustrated-Lewis-pair approach to catalytic reduction of alkynes to cis-alkenes

Design principles in frustrated Lewis pair catalysis for the functionalization of carbon dioxide and heterocycles

Contact Info

Product

Resources

About