Sergei V. Fedorov, Valentin A. Semenov, Leonid B. Krivdin
{"title":"Computational NMR of Carbohydrates. 2. Allopyranoses: Theoretical Conformational Analysis and NMR Calculations","authors":"Sergei V. Fedorov, Valentin A. Semenov, Leonid B. Krivdin","doi":"10.1002/poc.70079","DOIUrl":"10.1002/poc.70079","url":null,"abstract":"<div>\u0000 \u0000 <p>Allose, an aldohexose sugar, is a rare natural monosaccharide that occurs in nature in the form of a 6-O-cinnamyl glycoside in the leaves of the African shrub <i>Protea rubropilosa</i>. It differs from glucose in the orientation of the hydroxyl group at the C-3 position, being thus the C-3 substituted epimer of glucopyranose. In this paper, a detailed theoretical modeling of <i>α</i>- and <i>β</i>-D-alloses was performed, including molecular dynamics (MD) simulations, high-level geometry optimizations, and GIAO-DFT NMR studies. Generally, a good correlation between calculated <sup>1</sup>H and <sup>13</sup>C NMR chemical shifts of the conformationally averaged <i>α</i>- and <i>β</i>-D-alloses against experiment was found. Based on the performed calculations, the optimal combination of functionals with basis sets for the geometry optimization (M06-2X/aug-pc-2) and NMR calculations (BHandHLYP/aug-pcSseg-2) for carbohydrates was suggested.</p>\u0000 </div>","PeriodicalId":16829,"journal":{"name":"Journal of Physical Organic Chemistry","volume":"39 5","pages":""},"PeriodicalIF":1.8,"publicationDate":"2026-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147686965","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Life and Science With Dr. Matthew Platz","authors":"Raymond P. Goodrich","doi":"10.1002/poc.70078","DOIUrl":"https://doi.org/10.1002/poc.70078","url":null,"abstract":"<p>In life, there are relationships that expand our minds and enhance our thinking in our profession. There are mentors who guide us through difficult problem-solving exercises in our profession and those who help us through those situations in life issues in general. Matthew Platz is the kind of person who has walked me through the science of photochemical reactions and also helped me to better understand the role of science and scientists in the world. Our decades long collaboration has led to multiple innovations in the use of chemistry to prevent transfusion transmitted diseases, with a global impact on blood safety and availability.</p>","PeriodicalId":16829,"journal":{"name":"Journal of Physical Organic Chemistry","volume":"39 5","pages":""},"PeriodicalIF":1.8,"publicationDate":"2026-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/poc.70078","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147585221","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
C. R. Gopika, John B. Kottooran, Siddarth S. Mampallil, C. Rajalakshmi, Jesly Jacob, Gopinathan Anilkumar, Vibin Ipe Thomas
{"title":"Deciphering the Mechanism Behind the Fe/I\u0000 \u0000 \u0000 \u0000 \u0000 \u0000 2\u0000 \u0000 \u0000 \u0000 $$ {}_2 $$\u0000 Catalyzed Ortoleva–King Type Reaction: A DFT Study","authors":"C. R. Gopika, John B. Kottooran, Siddarth S. Mampallil, C. Rajalakshmi, Jesly Jacob, Gopinathan Anilkumar, Vibin Ipe Thomas","doi":"10.1002/poc.70077","DOIUrl":"https://doi.org/10.1002/poc.70077","url":null,"abstract":"<div>\u0000 \u0000 <p>Imidazo[1,2-<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>α</mi>\u0000 </mrow>\u0000 <annotation>$$ alpha $$</annotation>\u0000 </semantics></math>]pyridine derivatives have garnered significant attention due to their diverse pharmacological applications, driving the development of several synthetic methodologies. Among the various strategies employed, transition metal–catalyzed condensation reactions, particularly those of the Ortoleva–King type, have emerged as a prominent approach for the synthesis of imidazo[1,2-<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>α</mi>\u0000 </mrow>\u0000 <annotation>$$ alpha $$</annotation>\u0000 </semantics></math>]pyridines. Despite the ongoing experimental studies, a detailed molecular mechanistic investigation of these transformations remain insufficiently elucidated. In this study, we present a comprehensive computational investigation of an Fe/I<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mrow></mrow>\u0000 <mrow>\u0000 <mn>2</mn>\u0000 </mrow>\u0000 </msub>\u0000 </mrow>\u0000 <annotation>$$ {}_2 $$</annotation>\u0000 </semantics></math> assisted Ortoleva–King type reaction, employing aminopyridine and acetophenone as substrates. Using density functional theory (DFT) calculations at the unrestricted M06-L/def2-SVP level of theory, we delineate a five-step mechanistic pathway: activation of the methyl group of acetophenone by aminopyridine in the presence of molecular iodine, nucleophilic addition of 2-aminopyridine, redox reaction, water-mediated cyclization to construct the imidazo core, and final dehydration to furnish the imidazo[1,2-<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>α</mi>\u0000 </mrow>\u0000 <annotation>$$ alpha $$</annotation>\u0000 </semantics></math>]pyridine scaffold. Particular emphasis is placed on elucidating the role of the iron cocatalyst, the surprising participation of water in promoting cyclization in a slightly polar medium such as chlorobenzene. We find that the presence of electron-withdrawing groups on substrates has a substantial role in increasing the plausibility of the reaction.</p>\u0000 </div>","PeriodicalId":16829,"journal":{"name":"Journal of Physical Organic Chemistry","volume":"39 5","pages":""},"PeriodicalIF":1.8,"publicationDate":"2026-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147615119","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Cláudio M. Nunes, A. J. Lopes Jesus, Tatiana Caneca, Gemma Aragay, Pablo Ballester, Rui Fausto
{"title":"Triplet 4-Nitrenemethyl-Pyridine-N-Oxide: A Model Alkyl Nitrene Isolated in Cryogenic Matrices","authors":"Cláudio M. Nunes, A. J. Lopes Jesus, Tatiana Caneca, Gemma Aragay, Pablo Ballester, Rui Fausto","doi":"10.1002/poc.70074","DOIUrl":"https://doi.org/10.1002/poc.70074","url":null,"abstract":"<p>Alkyl nitrenes are highly reactive intermediates that are particularly challenging to study experimentally. Here, we report the first investigation of the simplest triplet alkyl nitrene bearing a pyridine-<i>N</i>-oxide moiety. Direct irradiation (λ > 350 nm) of 4-azidomethyl-pyridine-<i>N</i>-oxide in an Ar matrix (15 K) generated the target triplet 4-nitrenemethyl-pyridine-<i>N</i>-oxide <sup><b>3</b></sup><b>2</b>, along with <i>E</i> and <i>Z</i> isomers of 4-iminomethyl-pyridine-<i>N</i>-oxide <b>3</b>. Results from subsequent irradiations (λ > 325 nm) enabled the discrimination of the IR spectroscopic signatures of these species, allowing their unequivocal identification with support from DFT-B3LYP computations. Triplet nitrene <sup><b>3</b></sup><b>2</b> was found to be stable in dark Ar matrices, demonstrating that quantum tunneling 1,2-H shift to imine <b>3</b> is not operative on the experimental timescale. Computations show that this reaction is thermodynamically favorable on the triplet surface but involves a high-energy barrier (~36 kcal mol<sup>−1</sup>), explaining the absence of H-tunneling. As the pyridine-<i>N</i>-oxide moiety can act as an anchoring site for complexation with calix[4]pyrrole derivatives, our findings open new perspectives for investigating alkyl nitrene reactivity and tunneling phenomena under supramolecular confinement conditions.</p>","PeriodicalId":16829,"journal":{"name":"Journal of Physical Organic Chemistry","volume":"39 5","pages":""},"PeriodicalIF":1.8,"publicationDate":"2026-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/poc.70074","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147566336","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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