Bent Bond/Antiperiplanar Hypothesis and the Chemical Reactivity of Annulenes

Deslongchamps, Ghislain; Deslongchamps, Pierre

doi:10.1021/acs.joc.0c01069

Cited by 13 publications

(6 citation statements)

References 52 publications

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“…Naturally, the double-bond-shift isomerization is a facile step ( int-3′ to int-4 ), without an energy barrier in a clearly exergonic step, Δ G = −6.8 kcal·mol –1 . This results also agree well with the previous calculation results . In contrast, direct formation of int-4 via hydride transfer to the alkenyl group of int-3 (1,4-addition) proceeds through a similar transition state TS 2 ’ , but the barrier is reduced by 1.3 kcal·mol –1 with respect to TS 2 .…”

supporting

confidence: 92%

syn-Selective Construction of Fused Heterocycles by Catalytic Reductive Tandem Functionalization of N-Heteroarenes

et al. 2021

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To date, numerous methods have been successfully developed to functionalize N-heteroaryl C–H bonds. In contrast, dearomative tandem functionalization of N-heteroarenes is still a subject to be explored. Reported herein is an example on reductive dearomatization-induced tandem functionalization of N-heteroarenes by ruthenium catalysis, which offers a general method for diastereoselective construction of fused heterocycles featuring a cyclic syn-N, O-acetal motif from N-heteroarenes, phenols, and paraformaldehyde. Mechanistic study reveals that the products are formed via a tandem sequence of pyridyl C3-benzylation and hydroxymethylation followed by C2-aryloxylation of N-heteroarenium salts, proceeding with broad substrate scope, good functional group tolerance, high atom efficiency, and applicability for postfunctionalization of some biomedical molecules.

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supporting

confidence: 92%

syn-Selective Construction of Fused Heterocycles by Catalytic Reductive Tandem Functionalization of N-Heteroarenes

et al. 2021

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“…E1, S N 1, E2, and S N 2 reactions in OC2 are taught using Organic ChemWare animations as a learning tool, in which an animation of the mechanism (with either arrows or molecular orbitals) is shown occurring in concert with the coordinate of the reaction displayed on an energy diagram at each point of the animation. Therefore, students have implicit opportunities to develop the ability to make connections between the corresponding elements of how organic reactions are represented using reaction mechanisms and how they are represented using RCDs.…”

Section: Methodsmentioning

confidence: 99%

Getting Past the Rules and to the WHY: Causal Mechanistic Arguments When Judging the Plausibility of Organic Reaction Mechanisms

2019

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Citizens in all roles need to be able to construct causal explanations of scientific phenomena and engage in coherent argumentation, supported by evidence and sound reasoning. These skills are needed in many contexts, from making everyday decisions to addressing complex global issues. One goal of instruction in this area is to get past assessment questions that can be answered using only memorized rules (e.g., SN1 reactions are favored with tertiary halide substrates), toward answers that require reasoning with evidence (why is an SN1 pathway favored under certain conditions?). Previous work has suggested that these reasoning skills may not be effectively taught, practiced, or learned in organic chemistry courses or directly assessed on exams. In this study, we explored students’ ability to construct scientific arguments using evidence in the context of organic reaction mechanisms, specifically when comparing two proposed reaction mechanisms, making a claim as to which was most plausible, and providing reasoning. We used a qualitative coding scheme to analyze (1) the features and concepts students discussed in their arguments on exams, including the concept of granularity, (2) the connections (links) made between features and concepts, (3) the modes of reasoning revealed in the arguments, and (4) how the ideas and claims were explicitly compared. We found that ∼60% of arguments with correct claims established causal relationships between the relative stability of the carbocation intermediates and the relative activation energy barriers to the formation of these intermediates. However, the vast majority of students did not go to sufficient granularity to meet the expectations in the course, which they could have done by invoking Hammond’s postulate and hyperconjugation in their arguments. Incorrect claims were often supported by causal arguments but these arguments were incorrectly based on drawing a causal relationship between the relative steric hindrance of the starting materials and activation energy. Over 60% of students provided a linear causal mechanistic argument to justify their claim, independent of whether their claims were correct. Over 90% of arguments at least partially compared key concepts explicitly, with over 20% doing so completely. The findings suggest that the majority of students in this study understood the need to provide cause-and-effect relationships to justify their answer, beyond identifying reaction features and their effects; however, students may have struggled to identify which features of those molecules were relevant.

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“…Transannular versions of the archetypical Diels–Alder reaction have been explored and this reaction was used as useful model to understand the behavior of macrocyclic substrates towards transannular processes. Early reports by Deslongchamps 4 already established the critical role played by the conformational constraints of the macrocycle at the transition state, taking into account that the substrate needs to adopt a situation in which the diene moiety stands in a s - cis conformation to be reactive. In this sense, although the Diels–Alder reaction is diastereospecific in nature, the endo / exo selectivity can be strongly dependent on the size and nature of the substituents placed on the starting material.…”

Section: Transannular Cycloadditions and Electrocyclizationsmentioning

confidence: 99%

Recent Developments in Transannular Reactions

Reyes¹,

Prieto²,

Carrillo³

et al. 2022

Synthesis

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Transannular reactions have shown a remarkable performance for the construction of polycyclic scaffolds from medium- or large sized cyclic molecules in an unconventional manner. Recent examples of transannular reactions reported from 2011 have been reviewed, emphasizing the excellent performance of this approach when accessing the target compounds. This review also highlights how this methodology provides an alternative approach to other commonly used methodologies for the construction of cyclic entities such as cyclization or cycloaddition reactions

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Bent Bond/Antiperiplanar Hypothesis and the Chemical Reactivity of Annulenes

Cited by 13 publications

References 52 publications

syn-Selective Construction of Fused Heterocycles by Catalytic Reductive Tandem Functionalization of N-Heteroarenes

syn-Selective Construction of Fused Heterocycles by Catalytic Reductive Tandem Functionalization of N-Heteroarenes

Getting Past the Rules and to the WHY: Causal Mechanistic Arguments When Judging the Plausibility of Organic Reaction Mechanisms

Recent Developments in Transannular Reactions

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