1,721,023 research outputs found
Polar organometallic chemistry meets deep eutectic solvents in flow
Full text linkPolar organometallic chemistry in water and deep eutectic solvents (DESs) have recently captured the attention of chemists. In this issue of Chem, Torrente-Murciano, Hevia, and co-workers pioneer the first continuous and safe handling of organometallic reagents in (aqueous) DESs with an easy setup and without clogging problems at room temperature
"Four-membered Rings with One Oxygen and One Nitrogen Atom" in "Comprehensive Heterocyclic Chemistry III" Volume 2 "Four-membered Heterocycles"
No full textRegio- and stereoselective lithiation of 2,3-diphenylaziridines: A multinuclear NMR investigation
No full text(Figure Presented) The α-lithiation-trapping sequence of trans-N-alkyl-2,3-diphenylaziridines (s-BuLi or s-BuLi/TMEDA), taking place with a stereochemistry which dramatically depends on the solvent coordinating ability (inversion of configuration in THF and retention in toluene), has been carefully investigated. 1H,13C, and 7Li multinuclear NMR investigations at low temperature suggest that two differently configured lithiated aziridines (monomeric cis-1-Li in THF and dimeric trans-1-Li in toluene) are involved. © 2008 American Chemical Society
Structural and synthetic insights into the chemistry of lithium tetraorganozincates
No full textMain group bimetallic complexes have emerged as powerful reagents in organometallic synthesis, exhibiting unique reactivity profiles that cannot be replicated by their homo-metallic components. This chapter focusses on a particular family of bimetallic reagents, namely higher order lithium zincates. Exhibiting the empirical formulation R4ZnLi2 (R = alkyl, aryl, alkynyl, etc.), these compounds have found widespread applications in cornerstone organic reactions such as deprotonative metalation, metal halogen exchange or C[sbnd]C bond forming processes. By switching on bimetallic cooperativity these reagents exhibit excellent functional group tolerance and regioselectivities while being kinetically activated in comparison with parent organozinc reagents R2Zn. Showcasing key selected examples here we provide an overview on the synthesis, structure, solution constitution and stability of these mixed lithium/zinc complexes and discuss their most representative applications in modern organic synthesis. A main aim of this chapter is to shed light on the close interplay between structure and reactivity in this family of mixed lithium/zinc reagents and how bimetallic cooperation can be maximized to develop more effective and regioselective synthetic protocols
Recent advances in metal-, organo-, and biocatalyzed one-pot tandem reactions under environmentally responsible conditions
Full text linkBecause of their handedness and wide scope, transitionmetal-,
organo-, and biocatalyzed tandem processes have
become routine and highly sought-after methodologies
because they dramatically increase synthetic efficiency, while
decreasing the number of laboratory operations, the quantities
of chemicals and solvents used, producing in a simpler way
highly complex organic molecules with the desired selectivity.
In this current opinion, recent examples of the use of metal-,
organo-, and biocatalyzed tandem processes run under environmentally
responsible conditions (e.g., use of water, biobased
solvents, or without additional solvents) are showcased,
highlighting practical and valuable aspects
Metalation of 2-chloromethyl-2-oxazolines: Synthesis of 1,2,3-tris(oxazolinyl)cyclopropanes and derivatives
No full text2-Chloromethyl-2-oxazoline converts cleanly into trans-1,2,3-tris(oxazolinyl)cyclopropane upon treatment with strong bases such as LDA or KN(SiMe3)2. Deprotonation of the above cyclopropane followed by the addition of electrophiles allows the preparation of more functionalized tris-(oxazolinyl)cyclopropanes
Regio- and stereoselective lithiation and electrophilic substitution reactions of N-alkyl-2,3-diphenylaziridines: Solvent effect
No full textThe lithiation reaction of cis- and trans-N-alkyl-2,3-diphenylaziridines has been investigated. While cis-diphenylaziridines do not undergo any lithiation upon treatment with organolithiums, the lithiation reaction of the trans counterparts is completely α-regioselective and the stereochemical course of the lithiation-trapping sequence is solvent dependent: inversion of configuration in coordinating solvents (THF or toluene/crown ether) and retention in hexane, ether, or toluene. The preparation of stereodefined functionalized N-alkyl-2,3-diphenylaziridines is described. © 2007 American Chemical Society
Directed ortho lithiation of N-alkylphenylaziridines
No full text(Chemical Equation Presented) The ortho lithiation-trapping sequence of phenylaziridines is described. This methodology, which counts on the ability of the aziridino group to act as a directed metalation group (DMG), provides an easy access to functionalized arylaziridines as well as to phthalans and phthalides. The importance of the aziridine N-substituent in this DoM reaction is stressed as well. © 2005 American Chemical Society
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