Intramolecular [2+2] cycloadditions of Group IV metal-imido complexes. Applications to the synthesis of dihydropyrrole and tetrahydropyridine derivatives

McGrane, Paul; Jensen, Michael D.; Livinghouse, Tom

doi:10.1021/ja00039a087

Cited by 213 publications

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“…The rate and concentration data are listed in Table S-13 in the Supporting Information. The data obtained for this system were consistent with the rate law given in eq 8, but once again only the regime rate = k 5 k 8 8b 5a / (k 7 3b + k 8 5a ) (8) in which k 8 [5a] ≫ k 7 [3a] could be accessed (i.e., the reaction was zero-order in [5a]). The experimentally derived value of k 5 = (2.00 ± 0.02) × 10 −3 s −1 was obtained.…”

Section: Kinetic Analysis Of the Reaction Between Diazametallacycle Csupporting

confidence: 77%

“…These data (see Table S-12 in the Supporting Information) are consistent with the rate law described in eq 7, with k 4 = (2.3 ± 0.02) × 10 −3 s −1 . For this rate = k 4 k 8 8a 5a / (k 6 3a + k 8 5a ) (7) system, k 8 /k 6 could not be obtained from the kinetic study due to the inaccessibility of the region in which k 6 …”

Section: Kinetic Analysis Of the Reaction Between 8a And Alkyne 5amentioning

confidence: 99%

“…The experimentally derived value of k 5 = (2.00 ± 0.02) × 10 −3 s −1 was obtained. Unfortunately, when we increased the concentration of added carbodiimide 3b in order to access the region in which k 7 [3a] ≫ k 8 [5a], side reactions occurred that prevented the collection of reliable kinetic data.…”

Section: Kinetic Analysis Of the Reaction Between Diazametallacycle Cmentioning

confidence: 99%

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Mechanistic Investigation of Cycloreversion/Cycloaddition Reactions between Zirconocene Metallacycle Complexes and Unsaturated Organic Substrates

Zuckerman

Bergman

2001

Organometallics

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Treatment of the diazametallacycle Cp 2 Zr(N(t-Bu)C=N(SiMe 3 )N(SiMe 3 )) (4a) with diphenylacetylene resulted in the formation of the azametallacyclobutene Cp 2 Zr(N(t-Bu)C(Ph)=C (Ph)) (6a) and Me 3 SiN=C=NSiMe 3 in high yield. A kinetic study using UV-vis spectroscopy was carried out on the transformation. Saturation kinetic behavior was observed for the system, which is supportive of a mechanism that involves a reversible formal [2 + 2] retrocycloaddition of 4a to generate the transient imido species Cp 2 Zr=N-t-Bu (7a) and Me 3 -SiN=C=NSiMe 3 . Trapping 7a with diphenylacetylene in an overall [2 + 2] cycloaddition reaction affords zirconacycle 6a. The study of cycloreversion/cycloaddition reactions between diazametallacycle complexes and diphenylacetylene was extended to other zirconocene systems. Detailed kinetic studies were performed for the exchange reactions between the diazametallacycle complexes Cp 2 Zr(N(2,6-Me 2 Ph)C=N(SiMe 3 )N(SiMe 3 )) (8a) and Cp 2 Zr-(N(2,6-Me 2 Ph)C=N(t-Bu)N(t-Bu)) (8b) with diphenylacetylene (5a) to give the corresponding azametallacyclobutene complex Cp 2 Zr(N(2,6-Me 2 Ph)C(Ph)=C(Ph)) (6c) and extruded carbodiimides (Me 3 SiN=C=NSiMe 3 for 8a and (t-Bu) N=C=N(t-Bu) for 8b). For both systems, the reactions were found to be first order in metallacycle and zero order in alkyne. Treatment of the diazametallacycle complexes Cp 2 Zr(N(2,6-i-Pr 2 Ph)C=N (Cyc)N(Cyc)) (9a) and Cp 2 Zr-(N(2,6-i-Pr 2 Ph)C=N(i-Pr 2 )N(i-Pr 2 )) (9b) with alkyne 5a resulted in the formation of the six-membered zirconacycles 10a,b, respectively, upon heating at 75 °C. The products 10a,b are generated from the overall insertion of alkyne 5a into the nitrogen-carbon bond of the zirconium-containing diazacyclobutane. Complex 10a has been characterized by an X-ray crystallographic study. When the azacyclobutene Cp 2 Zr(N(2,6-i-Pr 2 Ph)C(Ph)=C(Ph)) (6e) was treated with CycN=C=NCyc or (i-Pr)N=C=N(i-Pr), the same six-membered zirconacycle complexes 10a,b were obtained. Kinetic analysis of the reaction of 6e and (i-Pr)N=C=N(i-Pr) to yield 10b supports an associative process wherein alkyne 5a directly inserts into the zirconium-carbon bond of 6e. The diazametallacycle complex 4a underwent a stoichiometric metathetical exchange with symmetrical carbodiimides RN=C=NR (R = p-Tol, m-Tol, i-Pr, Cyc) to generate new cyclic zirconocene complexes and Me 3 SiN=C=NSiMe 3 . Kinetic studies were carried out on the exchange reaction between 4a and (m-Tol)N=C=N(m-Tol) to form 4e and Me 3 SiN=C=NSiMe 3 . The experimental rate data obtained are consistent with a dissociative mechanism. Additionally, the saturation rate constant derived for this system from the data is the same (within experimental error) as the saturation rate constant obtained from the kinetic study of 4a and diphenylacetylene to form 6a and Me 3 SiN=C=NSiMe 3 . These findings provide additional support for a dissociative mechanistic pathway in the exchange reactions, since the rate constant in the formal [2 + 2] retrocycloaddition † This paper is dedic...

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Section: Kinetic Analysis Of the Reaction Between Diazametallacycle Csupporting

confidence: 77%

Section: Kinetic Analysis Of the Reaction Between 8a And Alkyne 5amentioning

confidence: 99%

Section: Kinetic Analysis Of the Reaction Between Diazametallacycle Cmentioning

confidence: 99%

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Mechanistic Investigation of Cycloreversion/Cycloaddition Reactions between Zirconocene Metallacycle Complexes and Unsaturated Organic Substrates

Zuckerman

Bergman

2001

Organometallics

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“…Transition metals have been workhorse elements in many commercialized catalytic processes that include hydrogenations, hydroformylations, acetic acid production, and other C-C and C-H bond forming processes. [1][2][3][4][5] Although carbon-oxygen, carbon-nitrogen, or carbon-sulfur bonds are found in the majority of important organic molecules, catalytic organometallic reaction chemistry that leads to the formation of carbon-heteroatom bonds is less common than that forming carbon-carbon and carbon-hydrogen bonds. Transition metal h 3 -allyl complexes, as well as transition metal s-alkyl complexes, play important roles as active species and key intermediates in many reactions catalyzed by transition metal complexes.…”

mentioning

confidence: 99%

“…Using cinnamyl alcohol (2b) as allylating agent worked well with acidic and less nucleophilic anilines (entries, 2,5,8,11,13,15). The sterically more demanding 2-cyclohexenol (2c), was an inefficient allylation reagent for 1a and for the more acidic anilines, although at reflux temperature (entries 3,6,9,12,14,16). Reaction of 2c with steric constraints amines 1a-c gave the worst yields.…”

mentioning

confidence: 99%

Palladium-Catalyzed Allylation of Acidic and Less Nucleophilic Anilines Using Allylic Alcohols Directly

Hsu

Gan

Yang

2005

CHEMICAL & PHARMACEUTICAL BULLETIN

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A principal goal of organometallic chemistry is the catalytic synthesis of organic compounds by using the chemistry of organic ligands covalently bound to transition metals. Most organometallic chemistry has focused on complexes with covalent metal-carbon or metal-hydrogen bonds. Transition metals have been workhorse elements in many commercialized catalytic processes that include hydrogenations, hydroformylations, acetic acid production, and other C-C and C-H bond forming processes. [1][2][3][4][5] Although carbon-oxygen, carbon-nitrogen, or carbon-sulfur bonds are found in the majority of important organic molecules, catalytic organometallic reaction chemistry that leads to the formation of carbon-heteroatom bonds is less common than that forming carbon-carbon and carbon-hydrogen bonds. Transition metal h 3 -allyl complexes, as well as transition metal s-alkyl complexes, play important roles as active species and key intermediates in many reactions catalyzed by transition metal complexes.6) The palladium-catalyzed allylation is an established, efficient, and highly stereo-and chemoselective method for C-C, C-N, and C-O bond formation, which has been widely applied to organic chemistry. [7][8][9][10] The processes have been shown to proceed by attack of nucleophiles on intermediate h 3 -allylpalladium(II) complexes generated by oxidative addition of allylic compounds including halides, [11][12][13] esters, [14][15][16][17][18][19][20][21][22][23][24][25][26] carbonates, [27][28][29][30][31][32][33][34][35][36] carbamates, [37][38][39] phosphates, [40][41][42] and related derivatives [43][44][45][46][47][48][49] to a Pd(0) complex. Because these substrates are synthesized from the corresponding allylic alcohols, palladium-catalyzed conversion of allylic alcohols directly into allylation products are highly desirable, especially from the viewpoint of the atom economy. 50,51) For achieving the palladium-catalyzed C-O bond cleavage of allylic alcohols, various other processes to facilitate the bond cleavage have been reported. 52) These processes include conversion of allylic alcohols into the esters of inorganic acids (e.g., SnCl 2 61-64) ). However, there have been only limited and sporadic reports dealing with the direct cleavage of the C-O bond in allylic alcohols on interaction with a transition metal complex. [65][66][67][68][69][70][71][72] Successful applications using allylic alcohols directly in catalytic processes are even more limited. This apparently stems from the poor capability of a nonactivated hydroxyl to serve as a leaving group. 59,60) We have recently reported our attempts and some successful applications of a process involving the C-O bond cleavage with direct use of allylic alcohols catalyzed by palladium complexes. [73][74][75][76] Herein, we report the application of this methodology to the palladium-catalyzed allylation of acidic and less nucleophilic anilines 77-80) using allylic alcohols directly. The allylation process is straightforward. We studied the reactions of acidic and less nucl...

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Catalysis as a key technology for the environmentally benign synthesis of amines and amino acids

Beller

1999

Med. Res. Rev.

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Intramolecular [2+2] cycloadditions of Group IV metal-imido complexes. Applications to the synthesis of dihydropyrrole and tetrahydropyridine derivatives

Cited by 213 publications

References 0 publications

Mechanistic Investigation of Cycloreversion/Cycloaddition Reactions between Zirconocene Metallacycle Complexes and Unsaturated Organic Substrates

Mechanistic Investigation of Cycloreversion/Cycloaddition Reactions between Zirconocene Metallacycle Complexes and Unsaturated Organic Substrates

Palladium-Catalyzed Allylation of Acidic and Less Nucleophilic Anilines Using Allylic Alcohols Directly

Catalysis as a key technology for the environmentally benign synthesis of amines and amino acids

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