Elements of an EffectiveResearch Presentation

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Tandem application of C-C bond-forming reactions with reductive ozonolysis

Several variants of reductive ozonolysis, defined here as the in situ generation of aldehydes or ketones during ozonolytic cleavage of alkenes, are demonstrated to work effectively in tandem with a number of C-C bond-forming reactions. For reactions involving basic nucleophiles (1,2- addition of Grignard reagents, Wittig or Horner-Emmons olefinations, and directed Aldol reactions of lithium enolates) the one-pot process offers a rapid and high-yielding alternative to traditional two-step protocols

Pyridine is an organocatalyst for the reductive ozonolysis of alkenes

Whereas the cleavage of alkenes by ozone typically generates peroxide intermediates that must be decomposed in an accompanying step, ozonolysis in the presence of pyridine directly generates ketones or aldehydes through a process that neither consumes pyridine nor generates any detectable peroxides. The reaction is hypothesized to involve nucleophile-promoted fragmentation of carbonyl oxides via formation of zwitterionic peroxyacetals

Tandem application of C-C bond-forming reactions with reductive ozonolysis

Several variants of reductive ozonolysis, defined here as the in situ generation of aldehydes or ketones during ozonolytic cleavage of alkenes, are demonstrated to work effectively in tandem with a number of C-C bond-forming reactions. For reactions involving basic nucleophiles (1,2- addition of Grignard reagents, Wittig or Horner-Emmons olefinations, and directed Aldol reactions of lithium enolates) the one-pot process offers a rapid and high-yielding alternative to traditional two-step protocols

The Peroxide: An Underutilized but Highly Advantageous Functional Group

Peroxides are members of a class of underutilized but highly advantageous functional groups. The peroxide functionality has significant biological and medicinal applications concerning natural and synthetic products. Peroxides are also versatile synthetic intermediates able to serve as precursors for a multitude of functional groups. Transformations exploiting the reactive O-O bond of peroxides to generate a multitude of products, via ozonolysis and oxacycle synthesis, are the focus of this work. The reaction of ozone with alkenes, ozonolysis, is used in organic synthesis as a means for controlled oxidative cleavage. The traditional approach to ozonolysis generates, as products, a class of peroxides known as secondary ozonides. The secondary ozonide must be subjected to a subsequent synthetic step to convert it into the desired product. The secondary ozonide and other peroxide-containing products of ozonolysis are often unstable towards self-accelerating decomposition reactions. An attractive alternative to a traditional stepwise approach would involve in situ capture of the carbonyl oxide intermediates. Ozonolysis in the presence of pyridine involves an unprecedented organocatalyzed decomposition of carbonyl oxides via the formation and fragmentation of zwitterionic peroxyacetals. The overall process is fast, general, and high-yielding route to aldehydes and/or ketones. Oxacycles, cyclic ethers, are an important functionality found in natural products. C-O bond formation is usually based on attack by a nucleophilic oxygen onto an electrophilic carbon. The converse of this strategy, attack of a carbanion on to an electrophilic oxygen, has essentially been unexplored for intramolecular reactions. Electrophilic acting peroxide oxygen atoms can be utilized to form oxacycles, including oxetanes, aryl ethers, and spirocycles. Applications of this chemistry are directly applicable to natural product synthesis and towards the synthesis of the oxetene functionality

Oxacycle Synthesis via Intramolecular Reaction of Carbanions and Peroxides

The intramolecular reaction of dialkyl peroxides with carbanions, generated via chemoselective metal-heteroatom exchange or deprotonation, provides a new approach to cyclic ethers. Applied in tandem with C–C bond formation, the strategy enables a one-step annelation to form oxaospirocycles

Tandem Application of C–C Bond-Forming Reactions with Reductive Ozonolysis

Several variants of reductive ozonolysis, defined here as the in situ generation of aldehydes or ketones during ozonolytic cleavage of alkenes, are demonstrated to work effectively in tandem with a number of C–C bond-forming reactions. For reactions involving basic nucleophiles (1,2-addition of Grignard reagents, Wittig or Horner–Emmons olefinations, and directed aldol reactions of lithium enolates), the one-pot process offers a rapid and high-yielding alternative to traditional two-step protocols

Pyridine Is an Organocatalyst for the Reductive Ozonolysis of Alkenes

Whereas the cleavage of alkenes by ozone typically generates peroxide intermediates that must be decomposed in an accompanying step, ozonolysis in the presence of pyridine directly generates ketones or aldehydes through a process that neither consumes pyridine nor generates any detectable peroxides. The reaction is hypothesized to involve nucleophile-promoted fragmentation of carbonyl oxides via formation of zwitterionic peroxyacetals