The Experts below are selected from a list of 1914 Experts worldwide ranked by ideXlab platform
Hélène Lebel - One of the best experts on this subject based on the ideXlab platform.
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mild and efficient one pot Curtius Rearrangement preparation of n tert butyl adamantanyl 1 yl carbamate
Organic Syntheses, 2009Co-Authors: Olivier Leogane, Hélène LebelAbstract:N-tert-Butyl adamantan-1-yl-carbamate Sodium azide Adamantine-1-carboxylic acid Tetra-n-butyl ammonium bromide Zinc triflate Di-tert-butyl dicarbonate Keywords: Curtius Rearrangement; one-pot preparation; acyl azides; isocyanate; carboxylic acids malonate derivatives; carbamates; waste disposal; safety
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Organic Syntheses - Mild and Efficient One‐Pot Curtius Rearrangement: Preparation of N‐tert‐Butyl Adamantanyl‐1‐Yl‐Carbamate
Organic Syntheses, 2009Co-Authors: Olivier Leogane, Hélène LebelAbstract:N-tert-Butyl adamantan-1-yl-carbamate Sodium azide Adamantine-1-carboxylic acid Tetra-n-butyl ammonium bromide Zinc triflate Di-tert-butyl dicarbonate Keywords: Curtius Rearrangement; one-pot preparation; acyl azides; isocyanate; carboxylic acids malonate derivatives; carbamates; waste disposal; safety
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Curtius Rearrangement of aromatic carboxylic acids to access protected anilines and aromatic ureas.
Organic letters, 2006Co-Authors: Hélène Lebel, Olivier LeoganeAbstract:The reaction of a chloroformate or di-tert-butyl dicarbonate and sodium azide with an aromatic carboxylic acid produces the corresponding acyl azide, presumably through the formation of an azidoformate. The acyl azide undergoes a Curtius Rearrangement to form an isocyanate derivative which is trapped either by an alkoxide or by an amine to form the aromatic carbamate or urea. The reaction conditions are compatible with a variety of functional groups and allow the synthesis of a number of aniline derivatives containing alkyl, halide, nitro, ketone, ether, and thioether substituents.
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Boc-protected amines via a mild and efficient one-pot Curtius Rearrangement.
Organic letters, 2005Co-Authors: Hélène Lebel, Olivier LeoganeAbstract:The reaction of a carboxylic acid with di-tert-butyl dicarbonate and sodium azide allowed the formation of an acyl azide intermediate, which undergoes a Curtius Rearrangement in the presence of tetrabutylammonium bromide and zinc(II) triflate. The trapping of the isocyanate derivative in the reaction mixture led to the desired tert-butyl carbamate in high yields at low temperature. These reaction conditions are compatible with a variety of substrates, including malonate derivatives, which provide access to protected amino acids.
Olivier Leogane - One of the best experts on this subject based on the ideXlab platform.
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mild and efficient one pot Curtius Rearrangement preparation of n tert butyl adamantanyl 1 yl carbamate
Organic Syntheses, 2009Co-Authors: Olivier Leogane, Hélène LebelAbstract:N-tert-Butyl adamantan-1-yl-carbamate Sodium azide Adamantine-1-carboxylic acid Tetra-n-butyl ammonium bromide Zinc triflate Di-tert-butyl dicarbonate Keywords: Curtius Rearrangement; one-pot preparation; acyl azides; isocyanate; carboxylic acids malonate derivatives; carbamates; waste disposal; safety
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Organic Syntheses - Mild and Efficient One‐Pot Curtius Rearrangement: Preparation of N‐tert‐Butyl Adamantanyl‐1‐Yl‐Carbamate
Organic Syntheses, 2009Co-Authors: Olivier Leogane, Hélène LebelAbstract:N-tert-Butyl adamantan-1-yl-carbamate Sodium azide Adamantine-1-carboxylic acid Tetra-n-butyl ammonium bromide Zinc triflate Di-tert-butyl dicarbonate Keywords: Curtius Rearrangement; one-pot preparation; acyl azides; isocyanate; carboxylic acids malonate derivatives; carbamates; waste disposal; safety
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Curtius Rearrangement of aromatic carboxylic acids to access protected anilines and aromatic ureas.
Organic letters, 2006Co-Authors: Hélène Lebel, Olivier LeoganeAbstract:The reaction of a chloroformate or di-tert-butyl dicarbonate and sodium azide with an aromatic carboxylic acid produces the corresponding acyl azide, presumably through the formation of an azidoformate. The acyl azide undergoes a Curtius Rearrangement to form an isocyanate derivative which is trapped either by an alkoxide or by an amine to form the aromatic carbamate or urea. The reaction conditions are compatible with a variety of functional groups and allow the synthesis of a number of aniline derivatives containing alkyl, halide, nitro, ketone, ether, and thioether substituents.
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Boc-protected amines via a mild and efficient one-pot Curtius Rearrangement.
Organic letters, 2005Co-Authors: Hélène Lebel, Olivier LeoganeAbstract:The reaction of a carboxylic acid with di-tert-butyl dicarbonate and sodium azide allowed the formation of an acyl azide intermediate, which undergoes a Curtius Rearrangement in the presence of tetrabutylammonium bromide and zinc(II) triflate. The trapping of the isocyanate derivative in the reaction mixture led to the desired tert-butyl carbamate in high yields at low temperature. These reaction conditions are compatible with a variety of substrates, including malonate derivatives, which provide access to protected amino acids.
Paul R. Hanson - One of the best experts on this subject based on the ideXlab platform.
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conformationally constrained α boc aminophosphonates via transition metal catalyzed Curtius Rearrangement strategies
Journal of Organic Chemistry, 2002Co-Authors: Joel D. Moore, Kevin T. Sprott, Paul R. HansonAbstract:A transition metal-catalyzed/Curtius Rearrangement sequence toward the development of conformationally constrained α-Boc-aminophosphonates 2−6 is described. An approach using the versatile tert-butylphosphonoacetate moieties 1a and 1b to derive an array of mono- and bicyclic α-Boc-aminophosphonate systems is presented. Conformational constraint is incorporated using either the ring-closing metathesis reaction catalyzed by the first generation Grubbs catalyst or intramolecular cyclopropanation mediated by Rh2(OAc)4. Using the tert-butyl ester functionality in 1a or 1b as a potential amino group, the Curtius Rearrangement provides an efficient route toward the target α-Boc-aminophosphonates.
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Conformationally constrained α-Boc-aminophosphonates via transition metal-catalyzed/Curtius Rearrangement strategies
Journal of Organic Chemistry, 2002Co-Authors: Joel D. Moore, Kevin T. Sprott, Paul R. HansonAbstract:A transition metal-catalyzed/Curtius Rearrangement sequence toward the development of conformationally constrained α-Boc-aminophosphonates 2?6 is described. An approach using the versatile tert-butylphosphonoacetate moieties 1a and 1b to derive an array of mono- and bicyclic α-Boc-aminophosphonate systems is presented. Conformational constraint is incorporated using either the ring-closing metathesis reaction catalyzed by the first generation Grubbs catalyst or intramolecular cyclopropanation mediated by Rh2(OAc)4. Using the tert-butyl ester functionality in 1a or 1b as a potential amino group, the Curtius Rearrangement provides an efficient route toward the target α-Boc-aminophosphonates.
Xiaoqing Zeng - One of the best experts on this subject based on the ideXlab platform.
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Decomposition of Sulfonyl Azide Isocyanate and Sulfonyl Diazide: The Oxygen-Shifted Curtius Rearrangement via Sulfonyl Nitrenes
The journal of physical chemistry. A, 2018Co-Authors: Xuelin Dong, Guohai Deng, Xiaoqing ZengAbstract:Sulfonyl azide isocyanate, (OCN)S(O)2N3, was prepared and characterized by IR (gas, matrix-isolation), Raman (liquid), and UV-vis spectroscopy. Upon flash vacuum pyrolysis (FVP) at ca. 1000 K, gaseous (OCN)S(O)2N3 decomposes completely and yields fragments N2, SO2, SO3, NCN, N3, NCO, CO, CN, and NO. In contrast, the azide splits off N2 and furnishes a transient triplet sulfonyl nitrene intermediate (OCN)S(O)2N upon a 266 nm laser irradiation in solid Ne-matrix at 2.8 K. Subsequent photolysis of the nitrene with visible light (λ = 380-450 nm) results in oxygen-shifted Curtius Rearrangement to a novel nitroso sulfoxide (OCN)S(O)NO. For comparison, the photodecomposition of the closely related sulfonyl diazide O2S(N3)2 in a solid Ar matrix was also studied. Upon an ArF excimer laser (193 nm) photolysis, O2S(N3)2 decomposes and yields N2, SO2, and OSNNO via the intermediacy of an elusive sufonyl nitrene N3S(O)2N. Further visible light irradiation (λ > 395 nm) leads to depletion of N3S(O)2N and OSNNO and concomitant formation of SO2 and N2. The identification of the intermediates in cryogenic matrixes by IR spectroscopy was supported by 15N-labeling experiments and quantum chemical calculations. The mechanism for the decomposition of both sulfonyl azides (OCN)S(O)2N3 and O2S(N3)2 was discussed on the basis of the observed intermediates and the calculated potential energy profiles.
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Decomposition of Sulfonyl Azide Isocyanate and Sulfonyl Diazide: The Oxygen-Shifted Curtius Rearrangement via Sulfonyl Nitrenes
2018Co-Authors: Xuelin Dong, Guohai Deng, Xiaoqing ZengAbstract:Sulfonyl azide isocyanate, (OCN)S(O)2N3, was prepared and characterized by IR (gas, matrix-isolation), Raman (liquid), and UV–vis spectroscopy. Upon flash vacuum pyrolysis (FVP) at ca. 1000 K, gaseous (OCN)S(O)2N3 decomposes completely and yields fragments N2, SO2, SO3, NCN, N3, NCO, CO, CN, and NO. In contrast, the azide splits off N2 and furnishes a transient triplet sulfonyl nitrene intermediate (OCN)S(O)2N upon a 266 nm laser irradiation in solid Ne-matrix at 2.8 K. Subsequent photolysis of the nitrene with visible light (λ = 380–450 nm) results in oxygen-shifted Curtius Rearrangement to a novel nitroso sulfoxide (OCN)S(O)NO. For comparison, the photodecomposition of the closely related sulfonyl diazide O2S(N3)2 in a solid Ar matrix was also studied. Upon an ArF excimer laser (193 nm) photolysis, O2S(N3)2 decomposes and yields N2, SO2, and OSNNO via the intermediacy of an elusive sufonyl nitrene N3S(O)2N. Further visible light irradiation (λ > 395 nm) leads to depletion of N3S(O)2N and OSNNO and concomitant formation of SO2 and N2. The identification of the intermediates in cryogenic matrixes by IR spectroscopy was supported by 15N-labeling experiments and quantum chemical calculations. The mechanism for the decomposition of both sulfonyl azides (OCN)S(O)2N3 and O2S(N3)2 was discussed on the basis of the observed intermediates and the calculated potential energy profiles
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contrasting photolytic and thermal decomposition of phenyl azidoformate the Curtius Rearrangement versus intramolecular c h amination
Journal of Physical Chemistry A, 2017Co-Authors: Huabin Wan, Qian Liu, Manabu Abe, Xiaoqing ZengAbstract:The decomposition of phenyl azidoformate, PhOC(O)N3, was studied by combining matrix isolation spectroscopy and quantum chemical calculations. Upon UV laser photolysis (193 and 266 nm), the azide isolated in cryogenic noble gas matrices (Ne and Ar, 2.8 K) decomposes into N2 and a novel oxycarbonylnitrene PhOC(O)N, which was identified by matrix-isolation IR spectroscopy (with 15N labeling) and EPR spectroscopy (|D/hc| = 1.620 cm–1 and |E/hc| = 0.024 cm–1). Subsequent visible-light irradiation (532 nm) causes Rearrangement of the nitrene into phenoxy isocyanate PhONCO with complex secondary fragmentation (PhO· + ·NCO) and radical recombination species in matrices. The observation of PhONCO provides solid evidence for the Curtius Rearrangement of phenyl azidoformate. In sharp contrast, flash vacuum pyrolysis (FVP) of PhOC(O)N3 at 550 K yields N2 and exclusively the intramolecular C–H amination product 3H-benzooxazol-2-one. FVP at higher temperature (700 K) leads to further dissociation into CO2, HNCO, and r...
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Contrasting Photolytic and Thermal Decomposition of Phenyl Azidoformate: The Curtius Rearrangement Versus Intramolecular C–H Amination
The journal of physical chemistry. A, 2017Co-Authors: Huabin Wan, Qian Liu, Manabu Abe, Xiaoqing ZengAbstract:The decomposition of phenyl azidoformate, PhOC(O)N3, was studied by combining matrix isolation spectroscopy and quantum chemical calculations. Upon UV laser photolysis (193 and 266 nm), the azide isolated in cryogenic noble gas matrices (Ne and Ar, 2.8 K) decomposes into N2 and a novel oxycarbonylnitrene PhOC(O)N, which was identified by matrix-isolation IR spectroscopy (with 15N labeling) and EPR spectroscopy (|D/hc| = 1.620 cm–1 and |E/hc| = 0.024 cm–1). Subsequent visible-light irradiation (532 nm) causes Rearrangement of the nitrene into phenoxy isocyanate PhONCO with complex secondary fragmentation (PhO· + ·NCO) and radical recombination species in matrices. The observation of PhONCO provides solid evidence for the Curtius Rearrangement of phenyl azidoformate. In sharp contrast, flash vacuum pyrolysis (FVP) of PhOC(O)N3 at 550 K yields N2 and exclusively the intramolecular C–H amination product 3H-benzooxazol-2-one. FVP at higher temperature (700 K) leads to further dissociation into CO2, HNCO, and r...
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Contrasting Photolytic and Thermal Decomposition of Phenyl Azidoformate: The Curtius Rearrangement Versus Intramolecular C–H Amination
2017Co-Authors: Huabin Wan, Qian Liu, Manabu Abe, Xiaoqing ZengAbstract:The decomposition of phenyl azidoformate, PhOC(O)N3, was studied by combining matrix isolation spectroscopy and quantum chemical calculations. Upon UV laser photolysis (193 and 266 nm), the azide isolated in cryogenic noble gas matrices (Ne and Ar, 2.8 K) decomposes into N2 and a novel oxycarbonylnitrene PhOC(O)N, which was identified by matrix-isolation IR spectroscopy (with 15N labeling) and EPR spectroscopy (|D/hc| = 1.620 cm–1 and |E/hc| = 0.024 cm–1). Subsequent visible-light irradiation (532 nm) causes Rearrangement of the nitrene into phenoxy isocyanate PhONCO with complex secondary fragmentation (PhO· + ·NCO) and radical recombination species in matrices. The observation of PhONCO provides solid evidence for the Curtius Rearrangement of phenyl azidoformate. In sharp contrast, flash vacuum pyrolysis (FVP) of PhOC(O)N3 at 550 K yields N2 and exclusively the intramolecular C–H amination product 3H-benzooxazol-2-one. FVP at higher temperature (700 K) leads to further dissociation into CO2, HNCO, and ring-contraction products. To account for the very different photolytic and thermal decomposition products, the underlying mechanisms for the Curtius Rearrangement (concerted and stepwise) of PhOC(O)N3 and the intramolecular C–H amination of the nitrene in both singlet and triplet states are discussed with the aid of quantum chemical calculations using the B3LYP, CBS-QB3, and CASPT2 methods
Stephen P. Waters - One of the best experts on this subject based on the ideXlab platform.
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Pyridone Annulation via Tandem Curtius Rearrangement/6π-Electrocyclization: Total Synthesis of (−)-Lyconadin C
2016Co-Authors: Xiayun Cheng, Stephen P. WatersAbstract:A concise, enantioselective total synthesis of the Lycopodium alkaloid (−)-lyconadin C was achieved in 12 steps and high overall yield. Key features include construction of a luciduline congener through Mannich-type cyclization and a one-pot, tandem Curtius Rearrangement/6π-electrocyclization to fashion the 2-pyridone system of lyconadin C
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Pyridone annulation via tandem Curtius Rearrangement/6π-electrocyclization: total synthesis of (-)-lyconadin C.
Organic letters, 2013Co-Authors: Xiayun Cheng, Stephen P. WatersAbstract:A concise, enantioselective total synthesis of the Lycopodium alkaloid (−)-lyconadin C was achieved in 12 steps and high overall yield. Key features include construction of a luciduline congener through Mannich-type cyclization and a one-pot, tandem Curtius Rearrangement/6π-electrocyclization to fashion the 2-pyridone system of lyconadin C.
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pyridone annulation via tandem Curtius Rearrangement 6π electrocyclization total synthesis of lyconadin c
Organic Letters, 2013Co-Authors: Xiayun Cheng, Stephen P. WatersAbstract:A concise, enantioselective total synthesis of the Lycopodium alkaloid (−)-lyconadin C was achieved in 12 steps and high overall yield. Key features include construction of a luciduline congener through Mannich-type cyclization and a one-pot, tandem Curtius Rearrangement/6π-electrocyclization to fashion the 2-pyridone system of lyconadin C.
