Journal ArticleDOI
Stereoelectronic power of oxygen in control of chemical reactivity: the anomeric effect is not alone
Igor V. Alabugin,Leah Kuhn,Michael G. Medvedev,Michael G. Medvedev,Nikolai V. Krivoshchapov,Nikolai V. Krivoshchapov,Vera A. Vil,Ivan A. Yaremenko,Patricia Mehaffy,Meysam Yarie,Alexander O. Terent'ev,Mohammad Ali Zolfigol +11 more
TLDR
In this article, the authors evaluate the fundamental connections between the anomeric effect and a broad variety of O-functional groups and highlight the vast implications of AE for the structure and reactivity of organic O-functionalities.Abstract:
Although carbon is the central element of organic chemistry, oxygen is the central element of stereoelectronic control in organic chemistry. Generally, a molecule with a C–O bond has both a strong donor (a lone pair) and a strong acceptor (e.g., a σ*C–O orbital), a combination that provides opportunities to influence chemical transformations at both ends of the electron demand spectrum. Oxygen is a stereoelectronic chameleon that adapts to the varying situations in radical, cationic, anionic, and metal-mediated transformations. Arguably, the most historically important stereoelectronic effect is the anomeric effect (AE), i.e., the axial preference of acceptor groups at the anomeric position of sugars. Although AE is generally attributed to hyperconjugative interactions of σ-acceptors with a lone pair at oxygen (negative hyperconjugation), recent literature reports suggested alternative explanations. In this context, it is timely to evaluate the fundamental connections between the AE and a broad variety of O-functional groups. Such connections illustrate the general role of hyperconjugation with oxygen lone pairs in reactivity. Lessons from the AE can be used as the conceptual framework for organizing disjointed observations into a logical body of knowledge. In contrast, neglect of hyperconjugation can be deeply misleading as it removes the stereoelectronic cornerstone on which, as we show in this review, the chemistry of organic oxygen functionalities is largely based. As negative hyperconjugation releases the “underutilized” stereoelectronic power of unshared electrons (the lone pairs) for the stabilization of a developing positive charge, the role of orbital interactions increases when the electronic demand is high and molecules distort from their equilibrium geometries. From this perspective, hyperconjugative anomeric interactions play a unique role in guiding reaction design. In this manuscript, we discuss the reactivity of organic O-functionalities, outline variations in the possible hyperconjugative patterns, and showcase the vast implications of AE for the structure and reactivity. On our journey through a variety of O-containing organic functional groups, from textbook to exotic, we will illustrate how this knowledge can predict chemical reactivity and unlock new useful synthetic transformations.read more
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Journal ArticleDOI
Anomeric effect, hyperconjugation and electrostatics: lessons from complexity in a classic stereoelectronic phenomenon
Igor V. Alabugin,Leah Kuhn,Nikolai V. Krivoshchapov,Nikolai V. Krivoshchapov,Patricia Mehaffy,Michael G. Medvedev,Michael G. Medvedev +6 more
TL;DR: In this paper, the authors use a classic conformational oddity, the anomeric effect, to discuss the value of identifying the key contributors to reactivity that can guide chemical predictions, and they show that the complete hyperconjugative model remains superior in explaining the interplay between structure and reactivity.
Journal ArticleDOI
Anodic electrosynthesis of MIL-53(Al)-N(CH2PO3H2)2 as a mesoporous catalyst for synthesis of novel (N-methyl-pyrrol)-pyrazolo[3,4-b]pyridines via a cooperative vinylogous anomeric based oxidation.
Sima Kalhor,Mahmoud Zarei,Mohammad Ali Zolfigol,Hassan Sepehrmansourie,Davood Nematollahi,Saber Alizadeh,Hu Shi,Jalal Arjomandi +7 more
TL;DR: In this article, the MIL-53(Al)-NH2 metal-organic frameworks (MOFs) were prepared based on the anodic electrosynthesis under green conditions.
Journal ArticleDOI
Catalytic synthesis of new pyrazolo [3,4-b] pyridine via a cooperative vinylogous anomeric-based oxidation
Hassan Sepehrmansourie,Mahmoud Zarei,Mohammad Ali Zolfigol,Saeedeh Babaee,Saeid Azizian,Sadegh Rostamnia +5 more
TL;DR: In this article , a nano-magnetic metal-organic framework based on Fe 3 O 4 (MIL-101(Cr)-N(CH 2 PO 3 ) 2 was synthesized and fully characterized, which was used as catalyst in the synthesis of pyrazolo [3,4- b ] pyridines as convenient medicine by condensation reaction of aldehydes, 5-(1 H -Indol-3-yl)-2 H -pyrazol 3-ylamine and 3-(cyanoacetyl)indole via a CVABO.
Journal ArticleDOI
MOF-Zn-NHC as an efficient N-heterocyclic carbene catalyst for aerobic oxidation of aldehydes to their corresponding carboxylic acids via a cooperative geminal anomeric based oxidation
TL;DR: In this paper, the MOF-Zn-NHC was used in the aerobic oxidation of aryl aldehydes to their corresponding carbocyclic acids via an anomeric based oxidation.
Journal ArticleDOI
A magnetic porous organic polymer: catalytic application in the synthesis of hybrid pyridines with indole, triazole and sulfonamide moieties
TL;DR: In this article , the synthesis and characterization of a triazine-based magnetic ionic porous organic polymer are reported. And the structure, morphology, and components of the prepared structure have been investigated with several spectroscopic and microscopic techniques such as FT-IR, EDX, elemental mapping, TGA/DTA, SEM, TEM, VSM, and BET analysis.
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