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Torsional control of stereoselectivities in electrophilic additions and cycloadditions to alkenes

Hao Wang, K. N. Houk
2014 Chemical Science  
Torsional effects control the π-facial stereoselectivities of a variety of synthetically important organic reactions.  ...  This review surveys theoretical calculations that have led to the understanding of the influence of the torsional effects on several types of stereoselective organic reactions, especially electrophilic  ...  Acknowledgments We are grateful to the National Institute of General Medical Sciences, National Institutes of Health, and the National Science Foundation for financial support of our research.  ... 
doi:10.1039/c3sc52538d pmid:24409340 pmcid:PMC3882201 fatcat:wf5li53qlrhhreeribbxtynvci

Axial Preferences in Allylation Reactions via the Zimmerman–Traxler Transition State

Tom Mejuch, Noga Gilboa, Eric Gayon, Hao Wang, K. N. Houk, Ilan Marek
2013 Accounts of Chemical Research  
CONSPECTUS The reaction of substituted allylmetal on prostereogenic carbonyl compound can give rise to up to two racemic diastereomers (syn and anti).  ...  Classically, when anti selectivity was observed from pure E-isomers while the Z-isomers exhibit syn-selectivity, the empirical Zimmerman -Traxler  ...  IM is holder of the Sir Michael and Lady Sobell Academic Chair.  ... 
doi:10.1021/ar4000532 pmid:23672428 pmcid:PMC3714348 fatcat:kjidm5ibgjb4vlv3flpqubcl2a

Origins of Stereoselectivities of Dihydroxylations of cis-Bicyclo[3.3.0]octenes

Hao Wang, Philipp Kohler, Larry E. Overman, K. N. Houk
2012 Journal of the American Chemical Society  
Torsional, electrostatic, and steric effects can all influence stereoselectivity, and the rigidity or flexibility of conformations of reactants provides a predictive guide to stereoselectivity.  ...  Torsional effects are largely responsible for the stereoselectivity encountered in the chromodorolide A synthesis. Many literature examples have been reported on related cases.  ...  Computations were performed on the National Science Foundation Terascale Computing System at the National Center for Supercomputing Applications (NCSA), and on the IDRE Hoffman2 cluster at UCLA.  ... 
doi:10.1021/ja3075538 pmid:22954350 pmcid:PMC3460691 fatcat:ybslfobew5gr7oagf32os65bc4

Asymmetric Conjugate Addition of Arylthiols to Enoates and Its Application to Organic Synthesis of Biologically Potent Compounds

2003 Yakugaku zasshi  
Stereoselectivity of both tandem inter-and intramolecular reaction is predictable by an allylic strain-controlled conformation model of the enolate, in which an approach of aldehyde takes place anti to  ...  lone pair-diŠerentiating coordination of a carbonyl oxygen to lithium are structural requirements of the substrates for high enantioselectivity.  ...  The stereoselectivity of this cyclization reaction was also predictable by the stereochemical model B where similar controlling factors are operative as shown in A (Scheme 5 and 7).  ... 
doi:10.1248/yakushi.123.9 pmid:12607940 fatcat:ikqix3wsunhtvnm2u2xcwt2bou

A Twist on Facial Selectivity of Hydride Reductions of Cyclic Ketones: Twist-Boat Conformers in Cyclohexanone, Piperidone, and Tropinone Reactions

Sharon R. Neufeldt, Gonzalo Jiménez-Osés, Daniel L. Comins, K. N. Houk
2014 Journal of Organic Chemistry  
Our results indicate that in certain cases, factors such as substrate conformation, nucleophile bulkiness, and remote steric features can affect stereoselectivity in ways that are difficult to predict  ...  by the general Felkin−Anh model.  ...  Notes The authors declare no competing financial interest.  ... 
doi:10.1021/jo5022635 pmid:25372509 pmcid:PMC4260662 fatcat:534hpxcqvbhcpblhek7t7s27mi

Stereoselective Intermolecular [2 + 2]-Photocycloaddition Reactions and Their Application in Synthesis

Thorsten Bach
1998 Synthesis (Stuttgart)  
For both reactions the regioselectivity and the simple diastereoselectivity which are relevant to the formation of a single product isomer are explained based on representative examples.  ...  Stereoselective intermolecular [2+2]-photocycloaddition reactions of alkenes and Paternò-Büchi reactions are reviewed.  ...  Induced Diastereoselectivity in Carbonyl Compounds Substrate-Induced Facial Diastereoselectivity For acyclic carbonyl compounds which bear a stereogenic center a significant differentiation of the diastereotopic  ... 
doi:10.1055/s-1998-2054 fatcat:lhlz7zg6ejgdjflxfvldihj4te

Reduction of cyclic anhydrides. II. Factors affecting regioselectivity of attack on the carbonyl group by metal hydrides

Margaret M. Kayser, Peter Morand
1978 Canadian journal of chemistry (Print)  
In the light of recent experimental findings and theories concerning metal hydride addition t o the carbonyl function, the electronic and steric factors influencing regioselectivity of cyclic anhydride  ...  Similar considerations may be extended to predict the major lactonic products in the reductions of various other unsymmetrical cyclic anhydrides. MARGARET M. KAYSER et PETER MORAND. Can. J.  ...  Wolkoff for helpful discussions and would like to thank the National Research Council of Canada for financial support.  ... 
doi:10.1139/v78-247 fatcat:im4tzdmrdbdrbktbismjarx76u

A Silyl Substituent Dictates the Pathway of a Concerted Electrocyclic Ring-opening of Cyclobutene

Masahiro Murakami, Yasufumi Miyamoto, Yoshihiko Ito
2002 Journal of Synthetic Organic Chemistry, Japan  
On the basis of this finding, a novel method for the stereoselective synthesis of functionalized 1, 3-butadiene derivatives from cyclobutenones was developed. 1. ( 24 ) J. Synth. Org. Chem., Jpn.  ...  in the inward transition state.  ...  In addition, the reaction of 11 (k = 0.53 11-1 at 140 °C) was faster than that of the carbon counterpart 9 (k = 0.32 h-1 at 140 °C). These results with 9 and 11 confirm the computational predictions.  ... 
doi:10.5059/yukigoseikyokaishi.60.1049 fatcat:dnwhb6esq5eaph7xe77p726i6i

The development and use of a general route to brassinolide, its biosynthetic precursors, metabolites and analogues

A. L. Hurski, Yu. V. Ermolovich, V. N. Zhabinskii, V. A. Khripach
2015 Organic and biomolecular chemistry  
A new method for the construction of steroid side chains through the addition of lithium salts of dithianes to a C-22 aldehyde was developed.  ...  It was applied for the preparation of brassinolide and related brassinosteroids.  ...  Ae de Groot (Wageningen) for helpful discussions and linguistic revision of the manuscript.  ... 
doi:10.1039/c4ob02197e pmid:25473936 fatcat:mn67rfbrpbachang5qxe662lhy

A Computational Investigation of the Uncatalysed and Water-Catalysed Acyl Rearrangements in Ingenol Esters

Asja A. Kroeger, Amir Karton
2018 Australian journal of chemistry (Print)  
We use double-hybrid density functional theory to explore the mechanisms for the uncatalysed and water-catalysed acyl migrations in a model ingenol ester.  ...  The proton transfers in the cyclisation and ring-opening steps may be catalysed by a water molecule. The water catalyst reduces the reaction barrier heights of these steps by over 90 kJ mol -1 .  ...  We also acknowledge system administration support provided by the Faculty of Science at UWA to the Linux cluster of the Karton group.  ... 
doi:10.1071/ch17501 fatcat:xcxf6cstpfehfbx6lo34f5bbba

Stereoselective Promiscuous Reactions Catalyzed by Lipases

Angela Patti, Claudia Sanfilippo
2022 International Journal of Molecular Sciences  
Despite the fact that new stereogenic carbons are formed in many of the tested reactions, the target products have been often obtained in racemic form and examples of an efficient asymmetric induction  ...  The ability of lipases to display activity beyond their physiological reactions, so-called "catalytic promiscuity", has gained increasing interest in the last two decades as an important tool for expanding  ...  of PPL or lipase A from A. niger (AL-AN), which displayed comparable activity and stereoselectivity in the model reaction with 4-nitrobenzaldehyde.  ... 
doi:10.3390/ijms23052675 pmid:35269815 pmcid:PMC8910291 fatcat:3noklfiganduxmcrah45dncqny

The 9-Phenyl-9-fluorenyl Group for Nitrogen Protection in Enantiospecific Synthesis

Essi J. Karppanen, Ari M. P. Koskinen
2010 Molecules  
However, at least some of the enantiopurity is lost in most of the existing reactions used in synthetic organic chemistry. This translates into unnecessary material losses.  ...  The phenylfluoren-9-yl (Pf) group, a relatively rarely used protecting group, has proven to be able to prevent racemization in α-amino compounds.  ...  Pf directs the regioselectivity of enolization and alkylation in both cyclic and acyclic compounds. The Pf protected amino ketones are deprotonated and alkylated solely at '-carbon.  ... 
doi:10.3390/molecules15096512 pmid:20877241 pmcid:PMC6257761 fatcat:txcr5kpcifgitazqb6ipcn6a4e

The boron-mediated ketone–ketone aldol reaction

Katie M. Cergol, Peter Turner, Mark J. Coster
2005 Tetrahedron Letters  
The reaction was most facile when cyclic ketones were used, with the highest yields obtained for the reaction of boron enolates with cyclohexanone as the acceptor. ---  ...  Transformation of a variety of ketones to their corresponding boron enolates with Chx 2 BCl/Et 3 N, followed by reaction with acceptor ketones in diethyl ether, and oxidation of the resultant boron aldolate  ...  Acknowledgments We thank the University of Sydney for funding, Dr Kelvin Picker for assistance with HPLC and Dr Ian Luck for assistance with 2D NMR experiments.  ... 
doi:10.1016/j.tetlet.2005.01.011 fatcat:k6owxbbkbna2tkxnvtv46jjalm

Stereoselective Synthesis of Tertiary Ethers through Geometric Control of Highly Substituted Oxocarbenium Ions

Lei Liu, Paul E. Floreancig
2010 Angewandte Chemie International Edition  
Herein, we describe a rare application of carbon-hydrogen bond functionalization for stereoselective syntheses of molecules that contain fully substituted carbon atoms.  ...  The approach is based on the development of a model that is able to predict the geometries of 1,1-disubstituted oxocarbenium ions involved in nucleophilic additions that form tertiary ethers with high  ...  A postulate for the steric differences of alkenes in models A and B is shown in Figure 2 .  ... 
doi:10.1002/anie.201002281 pmid:20629060 pmcid:PMC3140911 fatcat:gbo664wslbewncvl4ncm3bvmj4

Extended Enolates: Versatile Intermediates for Asymmetric C-H Functionalization via Noncovalent Catalysis

Claudio Palomo, Mikel Oiarbide
2021 Chemistry - A European Journal  
Catalyst-controlled functionalization of unmodified carbonyl compounds is a relevant operation in organic synthesis, especially when high levels of site- and stereoselectivity can be attained.  ...  This objective is now within reach for some subsets of enolizable substrates using various types of activation mechanisms.  ...  Acknowledgements We thank the University of the Basque Country UPV/EHU (UFI QOSYC 11/22), the Basque Government (grant IT-1236-19) and Ministerio de Ciencia e Innovation (grant PID2019-109633GBÀ C21),  ... 
doi:10.1002/chem.202100756 pmid:33961323 fatcat:xll76o7a4jc33cuczmc6w2vxki
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