Intramolecular Copper- and Rhodium-Mediated Carbenoid Reactions of α-(Propargyloxy)silyl-α-diazoacetates

Gettwert, Volker; Krebs, Fred C.; Maas, Gerhard

doi:10.1002/(sici)1099-0690(199905)1999:5<1213::aid-ejoc1213>3.0.co;2-u

Cited by 31 publications

(13 citation statements)

References 39 publications

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“…It was eventually discovered that carrying out the reaction between an alkyne and a diazocarbonyl compound in the presence of Rh or Cu catalyst at elevated temperatures allows for direct access to furans in a single step without isolation or even observation of cyclopropene intermediates. Direct preparation of furans via this method was reported by Ma [22], Basak [23], Lee [24], Davies [25], Padwa [26,27,28], and Maas [29]. At the same time, this process is often referred to as a catalytic version of [2+3] dipolar cycloaddition, and some authors even propose alternative mechanistic rationales that do not involve the cyclopropenation step.…”

Section: Methodsmentioning

confidence: 99%

Rearrangements of cyclopropenes into five-membered aromatic heterocycles: mechanistic aspect

Rubin

Ryabchuk

2012

Chem Heterocycl Comp

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This review covers rearrangements of cyclopropenes into aromatic five-membered heterocyclic compounds, namely furans and pyrroles; accompanied by small ring cleavage proceeding in the presence of catalytic amounts of transition metals, Lewis acids, or under UV irradiation. Due to significant strain in the small ring, cyclopropenes are characterized by increased energy and a conformationally constrained hydrocarbon skeleton, which chiefly defines their unusually high reactivity and selectivity in reactions atypical for other unsaturated compounds. The increased electronic density of the π-system of its strained double bond makes cyclopropene a very attractive substrate for π-philic transition metals [1]]. In turn, this opens avenues for extremely rich coordination chemistry for different types of catalytic rearrangements, as well as for addition and cycloaddition reactions. The important role of small cycles in the photochemistry of furans was first demonstrated in reports by Srinivason [2, 3] and van Tamelen [4,5], who discovered that the photo-rearrangement of 2-methylfurans 1 into 3-methylfurans 2 proceeds via a valent rearrangement forming 3-acylcyclopropene intermediate 3 (Scheme 1). In addition, in the reaction of furan 1а a competing photodecarbonylation leading to product 4 was detected, which confirmed the formation of intermediate 3-formylcyclopropene 3а (Scheme 1).Scheme 1

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Section: Methodsmentioning

confidence: 99%

Rearrangements of cyclopropenes into five-membered aromatic heterocycles: mechanistic aspect

Rubin

Ryabchuk

2012

Chem Heterocycl Comp

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“…Because compounds 1 and analogues are easy to make on scale, 6 − 11 safe to handle, and storable for months, this late-stage diversity aspect is a potential asset. 12 − 17 …”

Section: Introductionmentioning

confidence: 99%

From Serendipity to Rational Design: Heteroleptic Dirhodium Amidate Complexes for Diastereodivergent Asymmetric Cyclopropanation

et al. 2022

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A heteroleptic dirhodium paddlewheel complex comprising three chiral carboxylate ligands and one achiral acetamidate ligand has recently been found to be uniquely effective in catalyzing the asymmetric cyclopropanation of olefins with α-stannylated (silylated and germylated) α-diazoacetate derivatives. A number of control experiments in combination with detailed computational studies provide compelling evidence that an interligand hydrogen bond between the −NH group of the amidate and the ester carbonyl group of the reactive rhodium carbene intermediate plays a quintessential role in the stereodetermining transition state. The penalty for distorting this array outweighs steric arguments and renders two of the four conceivable transitions states unviable. Based on this mechanistic insight, the design of the parent catalyst is revisited herein: placement of appropriate peripheral substituents allows high levels of diastereocontrol to be imposed upon cyclopropanation, which the original catalyst lacks. Because the new complexes allow either trans- or cis-configured stannylated cyclopropanes to be made selectively and in excellent optical purity, this transformation also marks a rare case of diastereodivergent asymmetric catalysis. The products are amenable to stereospecific cross coupling with aryl halides or alkenyl triflates; these transformations appear to be the first examples of the formation of stereogenic quaternary carbon centers by the Stille reaction; carbonylative coupling is also achieved. Moreover, tin/lithium exchange affords chiral lithium enolates, which can be intercepted with a variety of electrophilic partners. The virtues and inherent flexibility of this new methodology are illustrated by an efficient synthesis of two salinilactones, extremely scarce bacterial metabolites with signaling function involved in the self-regulatory growth inhibition of the producing strain.

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“…The metal-catalyzed [2 + 1] cycloaddition of diazoalkanes with alkyne substrates is perhaps the most promising and leading route. Catalysts based on metals such as rhodium, − copper, − silver, , cobalt, and a few others − are useful for this purpose with even heme proteins and metal foils entering the fray in the search for better catalysts. , Metals also play a key role in cyclopropene utilizations as a synthone in organic chemistry, which either proceed with the preservation or opening of the three-membered carbocyclic ring. ,, Although the commonly invoked intermediates in quite a few of these metal-mediated processes are metal-cyclopropene complexes, , many of them are too reactive for direct investigations, and therefore reliable structural or spectroscopic information have been extremely limited. ,, Most notably, despite the multiple roles copper plays in cyclopropene chemistry from the synthesis, ,− , ring opening chemistry, ,− and carbometalations, , to being the target of ethylene antagonists (because of the ethylene binding copper-cofactor in plants), ,, there are no structurally authenticated η 2 -cyclopropene complexes of copper to date . Herein we report the isolation and complete characterization of three copper(I) η 2 -cyclopropene complexes, as well as a useful copper-mediated route to cyclopropenes.…”

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confidence: 99%

Isolable Copper(I) η²-Cyclopropene Complexes

2020

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Treatment of bis(pyrazolyl)borate ligand supported [(CF3)2Bp]Cu(NCMe) with 1,2,3-trisubstituted cyclopropenes produced thermally stable copper(I) η2-cyclopropene complexes amenable to detailed solution and solid-state analysis. The [(CF3)2Bp]Cu(NCMe) also catalyzed [2 + 1]-cycloaddition chemistry of terminal and internal alkynes with ethyl diazoacetate affording cyclopropenes, including those used as ligands in this work. The tris(pyrazolyl)borate [(CF3)2Tp]Cu(NCMe) is a competent catalyst for this process as well. The treatment of [(CF3)2Tp]Cu with ethyl 2,3-diethylcycloprop-2-enecarboxylate substrate gave an O-bonded rather than a η2-cyclopropene copper complex.

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Intramolecular Copper- and Rhodium-Mediated Carbenoid Reactions of α-(Propargyloxy)silyl-α-diazoacetates

Cited by 31 publications

References 39 publications

Rearrangements of cyclopropenes into five-membered aromatic heterocycles: mechanistic aspect

Rearrangements of cyclopropenes into five-membered aromatic heterocycles: mechanistic aspect

From Serendipity to Rational Design: Heteroleptic Dirhodium Amidate Complexes for Diastereodivergent Asymmetric Cyclopropanation

Isolable Copper(I) η²-Cyclopropene Complexes

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Intramolecular Copper- and Rhodium-Mediated Carbenoid Reactions of α-(Propargyloxy)silyl-α-diazoacetates

Cited by 31 publications

References 39 publications

Rearrangements of cyclopropenes into five-membered aromatic heterocycles: mechanistic aspect

Rearrangements of cyclopropenes into five-membered aromatic heterocycles: mechanistic aspect

From Serendipity to Rational Design: Heteroleptic Dirhodium Amidate Complexes for Diastereodivergent Asymmetric Cyclopropanation

Isolable Copper(I) η2-Cyclopropene Complexes

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Isolable Copper(I) η²-Cyclopropene Complexes