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546 results on '"RajanBabu, T. V."'

7. Activator-Free Single-Component Co(I)-Catalysts for Regio- and Enantioselective Heterodimerization and Hydroacylation Reactions of 1,3-Dienes. New Reduction Procedures for Synthesis of [L]Co(I)-Complexes and Comparison to in-situ Generated Catalysts

Author

Parsutkar, Mahesh M., Moore, Curtis E., and RajanBabu, T. V.

Subjects
Molecular Structure, Stereoisomerism, Cobalt, Article, Catalysis
Abstract

Although cobalt(I) bis-phosphine complexes have been implicated in many selective C-C bond-forming reactions, until recently relatively few of these compounds have been fully characterized or have been shown to be intermediates in catalytic reactions. In this paper we present a new practical method for the synthesis and isolation of several cobalt(I)-bis-phosphine complexes and their use in Co(I)-catalyzed reactions. We find that easily prepared (in situ generated or isolated) bis-phosphine and (2,6-N-aryliminoethyl)pyridine (PDI) cobalt (II) halide complexes are readily reduced by 1,4-bis-trimethylsilyl-1,4-dihydropyrazine or commercially available lithium nitride (Li3N), leaving behind only innocuous volatile byproducts. Depending on the structures of the bis-phosphines, the cobalt(I) complex crystallizes as a phosphine-bridged species [(P~P)(X)Co(I)[μ-(P~P)]Co(I)(X)(P~P)] or a halide-bridged species [(P~P)Co(I)[μ-(X)]2Co(I)(P~P)]. Because the side-products are innocuous, these methods can be used for the in-situ generation of catalytically competent Co(I) complexes for a variety of low-valent cobalt-catalyzed reactions of even sensitive substrates. These complexes are also useful for the synthesis of rare cationic [(P~P)Co(I)-η(4)-diene](+) X(−) or [(P~P)Co(I)-η(6)-arene](+) X(−) complexes, which are shown to be excellent single-component catalysts for the following regioselective reactions of dienes: heterodimerizations with ethylene or methyl acrylate, hydroacylation and hydroboration. The reactivity of the single-component catalysts with the in situ generated species are also documented.

Published
2022

18. A strategy for the preparation of catalysts with pendant quaternary ammonium groups using D-salicin

Author

Yan, Yuan-Yong and RajanBabu, T. V.

Subjects
Chemistry, Organic -- Research, Ammonium compounds -- Physiological aspects, Catalysts -- Research, Ligands -- Physiological aspects, Solution (Chemistry) -- Physiological aspects, Biological sciences, Chemistry
Abstract

Research has been conducted on the water-soluble chelating bis-phosphinite ligands. The preparation of these ligands from D-salicin has been carried out and the results are discussed.

Published
2001

22. Four Mechanistic Mysteries: The Benefits of Writing a Critical Review.

Author

Nugent, William A. and RajanBabu, T. V.

Subjects
*MYSTERY writing, *EPOXY compounds, *TITANIUM, *ORGANIC synthesis, *FREE radicals
Abstract

While writing a comprehensive review on the reactions of epoxides with titanium(III) reagents, we encountered a series of mechanistic puzzles. Using clues from the literature, many of which were not available at the time that the mysteries emerged, it was possible to demystify a number of these conundrums. We discuss four examples, which we believe will significantly change the way in which titanium(III) chemistry is practiced. Our experience underscores the importance of comprehensive and critical reviews in chemistry and the truism that the authors are prime beneficiaries of the review process. [ABSTRACT FROM AUTHOR]

Published
2021
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23. Catalytic enantioselective synthesis of cyclobutenes from alkynes and alkenyl derivatives

Author

RajanBabu, T. V.

Abstract

Discovery of enantioselective catalytic reactions for the preparation of chiral compounds from readily available precursors, using scalable and environmentally benign chemistry, can greatly impact their design, synthesis, and eventually manufacture on the scale. Functionalized cyclobutanes and cyclobutenes are important structural motifs seen in many bioactive natural products and pharmaceutically relevant small molecules. The simplest approach to make cyclobutenes is through an enantioselective [2 + 2]-cycloaddition between an alkyne and an alkenyl derivative. Known reactions of this class that give acceptable enantioselectivities are of very narrow scope and are strictly limited to activated alkynes and highly reactive alkenes. Here, we disclose a broadly applicable enantioselective [2 + 2]-cycloaddition between a wide variety of alkynes and alkenyl derivatives, two of the most abundant classes of organic precursors. The key cycloaddition reaction employs catalysts derived from readily synthesized ligands and an earth-abundant metal, cobalt. Over 50 different functionalized cyclobutenes with enantioselectivities in the range of 86u201397% ee are documented. In addition to this development, some of the novel observations made during these studies including a key role of a cationic Co (I)-intermediate, ligand and counter ion effects on the reactions, will be discussed.

Published
2017

30. Homogeneous two-component polycondensation without strict stoichiometric balance via the tsuji-trost reaction: remote control of two reaction sites by catalysis

Author

Nomura, Nobuyoshi, Tsurugi, Ko, RajanBabu, T. V., and Kondo, Tadao

Subjects
Catalysis -- Technology application, Polymers -- Chemical properties, Condensation (Meteorology) -- Research, Condensation -- Research, Technology application, Chemistry
Abstract

A study conducted revealed that a homogeneous two-component polycondensation reaction without strict stoichiometric balance could lead to polymers of high molecular weight by catalysis if certain structural reactivity criteria are met in the monomers.

Published
2004

31. Heterodimerization of Olefins. 1. hydrovinylation reactions of olefins that are amenable to asymmetric catalysis

Author

RajanBabu, T. V., Nomura, Nobuyoshi, Jin, Jian, Nandi, Malay, Park, Haengsoon, and Sun, Xiufeng

Subjects
Catalysis -- Research, Chemical reactions -- Research, Olefins -- Research, Biological sciences, Chemistry
Abstract

New protocols for a nearly quantitative and highly selective codimerization of ethylene and various functionalized vinylarenes are discovered, with the help of systematic examination of ligand and counterion effects. The effects of hemilabile coordination on the efficiency and selectivity of the reaction are discussed.

Published
2003

32. Asymmetric hydrovinylation reaction

Author

RajanBabu, T. V.

Subjects
Hydrogen, Chemical reactions -- Analysis, Chemical research -- Analysis, Chemistry
Abstract

The author reviews the publications on asymmetric hydrovinylation reaction. The topics include the history of this reaction, its mechanisms, and the improved procedures for the reaction.

Published
2003

34. Examining the Scope and Thermodynamics of Assembly in Nesting Complexes Comprising Molecular Baskets and TPA Ligands

Author

Zhiquan, Lei, Polen, Shane M., Hadad, Christopher M., RajanBabu, T. V., and Badjić, Jovica D.

Abstract

Molecular baskets capture various tris(2-pyridylmethyl)amine ligands, with and without zinc(II) cation, to form nesting complexes. The results of our computational (MD) and experimental (1H NMR/ITC) studies suggest that the assembly is driven by the hydrophobic effect with the charge of complementary molecular components playing an important role in the formation of nesting complexes. In brief, the complexation only takes place when the basket and the ligand carry either oppositely charged or noncharged groups.

Published
2024
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