Directed nitrile oxide cycloaddition reactions. The use of hydrogen bonding to direct regio- and stereochemistry in nitrile oxide cycloadditions with cyclopentenylamides

Curran, Dennis P.; Choi, Sung Mo; Gothe, Scott A.; Lin, Fu Tyan

doi:10.1021/jo00299a004

Cited by 38 publications

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“…One difference between these types of amides is the presence or absence of the amide hydrogen which can function as a hydrogen bond donor which may lead to a templating effect and, hence, affect the regiochemistry of the reaction. Curran has reported that allylic secondary amides can alter the regio- and diastereoselectivity of nitrile oxide cycloadditions . The authors proposed that the amide hydrogen forms a hydrogen bond with the oxygen of the nitrile oxide, thus leading to a preponderance (90:10 ratio) of the 5-substituted cycloadduct.…”

Section: Discussionmentioning

confidence: 99%

Unusual Regioselectivity of the Dipolar Cycloaddition Reactions of Nitrile Oxides and Tertiary Cinnamides and Crotonamides¹

Weidner‐Wells¹,

Fraga-Spano²,

Turchi³

1998

J. Org. Chem.

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Benzonitrile oxides undergo 1,3-dipolar cycloaddition reactions with methyl cinnamate to produce the 5-phenyl and 4-phenyl regioisomers in approximately an 80:20 ratio. However, use of N,N-diethylcinnamide as the dipolarophile unexpectedly resulted in the formation of the 5-phenyl and 4-phenyl regioisomers in a 23:77 ratio. Studies have shown that this phenomena occurs only for tertiary cinnamides. In addition, it has been demonstrated that the phenyl group of tertiary cinnamides is not essential for the reversal of regioselectivity since crotonamides produce the same results and trends as the cinnamides. However, since acrylates and acrylamides both produce the 5-carbonyl regioisomers, it can be concluded that the beta-substituent is playing a key role for the unexpected results by possibly increasing steric interactions between the dipole and dipolarophile in the transition state. Transition state energies were calculated for the regioisomeric cycloadduct pairs derived from several crotonamides as well as methyl crotonate. These calculations indicate that steric factors are indeed responsible for the reversal of regioselectivity.

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Section: Discussionmentioning

confidence: 99%

Unusual Regioselectivity of the Dipolar Cycloaddition Reactions of Nitrile Oxides and Tertiary Cinnamides and Crotonamides¹

Weidner‐Wells¹,

Fraga-Spano²,

Turchi³

1998

J. Org. Chem.

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“…Highly diastereoselective cycloaddition reactions of nitrile oxides to alkenes are rare . We believe the facial diastereoselectivity observed in the reaction of cyclopentenyl ureas such as 10 with nitrile oxides can be understood based on H-bonded direction of the cycloaddition step as depicted in V (Figure ).…”

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confidence: 97%

Diastereoselective Synthesis of Cyclopentanoids with Hydantoin and Isoxazoline Substituents

1998

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“…A series of 3-substituted cyclopentenes 32a ± p including amides 32f ± p have been studied as dipolarophiles; 53 variation of the amide acyl group made it possible to change the acidity of the proton in the amide substituent…”

Section: Cycloaddition Of Nitrile Oxides To Unsaturated Amines Amides...mentioning

confidence: 99%

Regio- and stereochemistry of 1,3-dipolar cycloaddition of nitrile oxides to alkenes

Litvinovskaya¹,

Хрипач²

2001

Russ. Chem. Rev.

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We prove that the Bohmian arrival time of the one-dimensional Schrödinger evolution violates the quadratic form structure on which Kijowski's axiomatic treatment of arrival times is based. Within Kijowski's framework, for a free right moving wave packet , the various notions of arrival time (at a fixed point x on the real line) all yield the same average arrival time t K ij ( ). We derive the inequality t B ( ) t K ij ( ) relating the average Bohmian arrival time to that of Kijowksi. We prove that t B ( ) < t K ij ( ) if and only if leads to position probability backflow through x.

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Directed nitrile oxide cycloaddition reactions. The use of hydrogen bonding to direct regio- and stereochemistry in nitrile oxide cycloadditions with cyclopentenylamides

Cited by 38 publications

References 0 publications

Unusual Regioselectivity of the Dipolar Cycloaddition Reactions of Nitrile Oxides and Tertiary Cinnamides and Crotonamides¹

Unusual Regioselectivity of the Dipolar Cycloaddition Reactions of Nitrile Oxides and Tertiary Cinnamides and Crotonamides¹

Diastereoselective Synthesis of Cyclopentanoids with Hydantoin and Isoxazoline Substituents

Regio- and stereochemistry of 1,3-dipolar cycloaddition of nitrile oxides to alkenes

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Directed nitrile oxide cycloaddition reactions. The use of hydrogen bonding to direct regio- and stereochemistry in nitrile oxide cycloadditions with cyclopentenylamides

Cited by 38 publications

References 0 publications

Unusual Regioselectivity of the Dipolar Cycloaddition Reactions of Nitrile Oxides and Tertiary Cinnamides and Crotonamides1

Unusual Regioselectivity of the Dipolar Cycloaddition Reactions of Nitrile Oxides and Tertiary Cinnamides and Crotonamides1

Diastereoselective Synthesis of Cyclopentanoids with Hydantoin and Isoxazoline Substituents

Regio- and stereochemistry of 1,3-dipolar cycloaddition of nitrile oxides to alkenes

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Unusual Regioselectivity of the Dipolar Cycloaddition Reactions of Nitrile Oxides and Tertiary Cinnamides and Crotonamides¹

Unusual Regioselectivity of the Dipolar Cycloaddition Reactions of Nitrile Oxides and Tertiary Cinnamides and Crotonamides¹