Synthesis of highly substituted oxetanes via [2+2] cycloaddition reactions of allenoates catalyzed by a guanidine Lewis base

Selig, Philipp; Turočkin, Aleksej; Raven, William

doi:10.1039/c3cc40855h

Cited by 38 publications

(17 citation statements)

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“…10). The charge analysis is consistent with the observation [35][36][37][43][44][45]47,48 that the [2 + 2] cycloaddition usually requires polar, unsaturated substrates, such as ketones or imines.…”

Section: Organic and Biomolecular Chemistry Papersupporting

confidence: 88%

“…19 An asymmetric variant of the phosphine-catalyzed [3 + 2] cyclization has been developed and successfully applied to the synthesis of complex natural products. [20][21][22][23][24][25][26][27][28][29][30][31] Nitrogenbased Lewis bases, such as 1,4-diazabicyclo[2.2.2]octane (DABCO), [32][33][34][35][36][37][38][39] quinuclidine derivatives, 39,[41][42][43][44] 4-(dimethylamino)pyridine (DMAP) 34,36 and guanidines, 45,46 have been found to catalyze the [2 + 4] cycloaddition of allenoates with enones [32][33][34][39][40][41][42] and the [2 + 2] addition with ketones 35,45,47 or imines 36,37,43,44,48 more recently. The first step of these N-catalyzed reactions is the formation of the LB•allenoate adduct as observed with the ph...…”

Section: Introductionmentioning

confidence: 99%

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A computational study of the activation of allenoates by Lewis bases and the reactivity of intermediate adducts

Huang

Lankau

2014

Org. Biomol. Chem.

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Several chemical properties of Lewis base-allenoate adducts (LB·allenoate), such as solvent effect, basicity, nucleophilicity and cycloaddition, are studied to provide a detailed foundation for the analysis of LB-catalyzed reactions of allenoates. The zwitterionic LB·allenoates formed between methyl allenoate and Lewis bases, such as N-heterocyclic carbenes (NHCs), phosphines, amines and aza-heterocycles, are studied at the M06-2X/6-31+G* level. The addition of the LBs to the allenoate can yield Z- or E-type adducts. The formation of the Z-type adducts is more favorable in the gas phase due to electrostatic interactions. The yield of the E-type adducts increases with the permittivity of the solvent. The lowest barriers for the addition and the most stable adducts are observed with NHCs as catalysts. It is also shown that the α-carbon atom of the allenic moiety in LB·allenoate is more nucleophilic than the γ-carbon atom. Aza-arenes, phosphines and NHCs stabilize the [3 + 2]-ylides formed by the cycloaddition of LB·allenoate to ethylene; therefore, these LBs thermodynamically support the [3 + 2] cycloadditions. The detailed analysis of [3 + 2]-, [2 + 4]-, [2 + 2]- and [2 + 2 + 2]-cycloadditions with enones/ketones shows that the amine-catalyzed reactions follow the kinetically preferred path, and that the exergonic formation of the P-ylide favors the [3 + 2] cycloaddition in the phosphine-catalyzed reaction. The thermodynamically preferred pathway is followed with NHCs whereas the high stability of NHC·allenoate adducts reduces the overall catalytic efficiency of NHCs.

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Section: Organic and Biomolecular Chemistry Papersupporting

confidence: 88%

Section: Introductionmentioning

confidence: 99%

A computational study of the activation of allenoates by Lewis bases and the reactivity of intermediate adducts

Huang

Lankau

2014

Org. Biomol. Chem.

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“…In the experiment, Lewis bases‐promoted annulations of allenoates with activated alkenes, imines, aldehydes, ketones, oxadiene, enynols, and dithioester have been studied. Applications of these annulations in chemical, pharmaceutical, and medical areas have also been achieved .…”

Section: Introductionmentioning

confidence: 99%

“…The most famous example is the phosphane-catalyzed [3 1 2] cycloaddition reactions of allenoates with activated alkenes, which has been reported by Lu and coworkers in 1995. [20] Since then, a large number of Lewis bases catalyzed annulation reactions of allenoates have been reported either experimentally or theoretically.In the experiment, Lewis bases-promoted annulations of allenoates with activated alkenes, [21][22][23][24] imines, [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40] aldehydes, [41,42] ketones, [43,44] oxadiene, [45] enynols, [46] and dithioester [47] have been studied. Applications of these annulations in chemical, pharmaceutical, and medical areas have also been achieved.…”

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confidence: 99%

Mechanisms of DABCO‐ and DMAP‐catalyzed [2 + 4] cycloaddition reactions of methylallenoate with methyleneindolonone: A DFT study

Liu

2017

Int J of Quantum Chemistry

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The mechanisms and stereoselectivities of the [2 + 4] cycloaddition reaction of methylallenoate R1 with methyleneindolonone R2 catalyzed by DABCO (Equation 1) and DMAP (Equation 2) organocatalysts have been examined with density functional theory (M06‐2X) calculations. Several possible reaction pathways (paths 1a, 1b, and 1c for Equation 1 and paths 2a and 2b for Equation 2) were located and compared. The results of our study reveal that for both reactions, three reaction stages have been characterized: nucleophilic addition of the catalyst (DABCO or DMAP) to R1 (Stage I), addition of the other reactant R2 (Stage II), intramolecular cycloaddition and liberation of the catalyst (DABCO or DMAP) afforded the final product (Stage III). For the DABCO‐catalyzed cycloaddition, we predict that path 1a leading to P(E) is the most energy favorable pathway among the three possible pathways. The carbon–carbon bond formation step is the rate‐determining step (ΔG‡=23.6 kcal/mol). With DMAP catalyst, the same reaction gave P(Z) as the major product. The barrier for the rate‐determining step (addition of R1 to DMAP) is 25.8 kcal/mol. The calculated results are in agreement with the experimental findings. Moreover, for both reactions, the analysis of global reactivity indexes has been carried out to examine the role of catalyst. The present study should provide a general mechanistic framework for the rational design of this kind of reactions.

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“…10 (E) TBD was found to be an exceptionally active catalyst for the cycloaddition of allenoate esters 11 and trifluoromethyl aryl ketones, enabling the preparation of very densely substituted oxetanes 12 in a diastereoselective manner. 11 The reaction required only short reaction times and worked well with γ-and even with α,γ-disubstituted allenoates. …”

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confidence: 99%

1,5,7-Triazabicyclo[4.4.0]dec-5-ene (TBD) as a Lewis Base

Turočkin

2014

Synlett

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This feature focuses on a reagent chosen by a postgraduate, highlighting the uses and preparation of the reagent in current research 894 spotlight 1,5,7-Triazabicyclo[4.4.0]dec-5-ene (TBD) as a Lewis Base Compiled by Aleksej Turočkin Aleksej Turočkin was born in 1986 in Nizhny Tagil, Russian Federation. He studied chemistry at Technische Universität München and carried out his master's thesis under the supervision of Professor Dr. Lukas Hintermann in 2011. After a research internship at Priaxon AG, he started his PhD in 2012 in the research group of Dr. Philipp Selig at RWTH Aachen University. His research focuses on the investigation of nucleophilic properties of guanidines and on the syntheses of chiral bicyclic guanidine organocatalysts.

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Synthesis of highly substituted oxetanes via [2+2] cycloaddition reactions of allenoates catalyzed by a guanidine Lewis base

Abstract: The first synthesis of highly substituted 3-alkyl-oxetan-2-ylidenes from allenoates was developed by using the bicyclic guanidine 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) as an exceptionally active nitrogen Lewis base catalyst.

Cited by 38 publications

References 26 publications

A computational study of the activation of allenoates by Lewis bases and the reactivity of intermediate adducts

A computational study of the activation of allenoates by Lewis bases and the reactivity of intermediate adducts

Mechanisms of DABCO‐ and DMAP‐catalyzed [2 + 4] cycloaddition reactions of methylallenoate with methyleneindolonone: A DFT study

1,5,7-Triazabicyclo[4.4.0]dec-5-ene (TBD) as a Lewis Base

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