The Application of Radiation Chemistry to Mechanistic Studies in Organic Chemistry

The allylation of aldehydes is a fundamental transformation in synthetic organic chemistry. Among the multitude of available reagents, especially allylsilanes have been established as preferred allyl source. As initially reported by Hosomi & Sakurai, these non-toxic and highly stable reagents add to carbonyls via an open transition state upon Lewis acid activation. Herein, we report a general strategy to access a variety of valuable homoallylic alcohols in opposite chemo- and diastereoselectivity to the established Hosomi–Sakurai conditions by switching to photocatalytic activation in combination with a closed transition state (Chromium catalysis). Moreover, this dual catalytic approach displays a straightforward way to introduce excellent levels of enantioselectivity and its mild conditions allow for a broad substrate scope including chiral boron-substituted products as a highlight. To emphasize the synthetic utility, our method was applied as the key step in the synthesis of a bioactive compound and in the late-stage functionalization of steroid derivatives. Detailed mechanistic studies and DFT calculations hint towards an unprecedented photo-initiated chain being operative.

Download Full-text

Mechanistic Studies on the Radiation Chemistry of Poly(hydroxybutyrate)

ACS Symposium Series - Irradiation of Polymers ◽

10.1021/bk-1996-0620.ch002 ◽

1996 ◽

pp. 11-27 ◽

Cited By ~ 9

Author(s):

Trudy Carswell-Pomerantz ◽

Limin Dong ◽

David J. T. Hill ◽

James H. O'Donnell ◽

Peter J. Pomery

Keyword(s):

Radiation Chemistry ◽

Mechanistic Studies

Download Full-text

William David Ollis. 22 December 1924 — 13 June 1999

Biographical Memoirs of Fellows of the Royal Society ◽

10.1098/rsbm.2001.0023 ◽

2001 ◽

Vol 47 ◽

pp. 395-413

Author(s):

G.M. Blackburn ◽

I.O. Sutherland

Keyword(s):

Organic Chemistry ◽

Natural Product ◽

Mechanistic Studies ◽

Natural Product Chemistry ◽

The 1950S ◽

The Uk ◽

Product Chemistry

David Ollis was one of the most influential and significant members of the group of British chemists who rose to prominence during the 1950s and 1960s. In common with other members of this group, he made important and lasting contributions to both the theory and the practice of his chosen discipline. Although the growth of natural product chemistry was less dramatic during the 1970s and beyond, he transposed his activities increasingly into mechanistic studies and so remained one of the leaders of chemistry in the UK. He occupied the Chair of Organic Chemistry at Sheffield University from 1963 to his retirement in 1990, and thereafter continued to be involved in chemistry through an honorary appointment at Birmingham University until his death in 1999.

Download Full-text

Manganese-Catalyzed Direct Olefination via an Acceptorless Dehydrogenative Coupling of Methyl Heteroarenes with Primary Alcohols

Synlett ◽

10.1055/s-0037-1610313 ◽

2018 ◽

Vol 30 (01) ◽

pp. 12-20 ◽

Cited By ~ 5

Author(s):

Biplab Maji ◽

Milan Barman ◽

Satyadeep Waiba

Keyword(s):

Organic Chemistry ◽

Energy Source ◽

Transition Metal ◽

Environmentally Benign ◽

Mechanistic Studies ◽

Primary Alcohols ◽

Dehydrogenative Coupling ◽

Synthetic Procedure ◽

Tremendous Progress ◽

Metal Catalyzed

Synthesis of olefins utilizing different catalytic strategies is an emerging topic in organic chemistry. However, despite of tremendous progress in the field the direct olefination of C(sp3)–H bonds using primary alcohols via an acceptorless dehydrogenative coupling (ADC) is not developed. Such an ADC reaction is highly environmentally benign as it produces dihydrogen and water as the sole byproducts. The liberated dihydrogen can potentially be used as an energy source. In this Synpact article, we present the recent development of ADC reaction as a tool to make unsaturated molecules and a summary of our recently developed synthetic procedure for the preparation of olefins employing an ADC reaction of methyl heteroarenes with alcohols. The catalyst development using an earth’s abundant metal manganese and the scope of such reaction is discussed.1 Introduction2 The Acceptorless Dehydrogenative Coupling as a Tool to Make Unsaturated Molecules3 Transition-Metal-Catalyzed Coupling of Alcohols with Methyl-Substituted Heteroarenes4 Development of the Manganese Catalyst for the Olefination of Methyl-Substituted Heteroarenes5 Scope and Limitation of the Manganese-Catalyzed Direct Olefination of Methyl-Substituted Heteroarenes6 Mechanistic Studies and Proposed Mechanism7 Conclusion

Download Full-text

Dialkyl dicyanofumarates and dicyanomaleates as versatile building blocks for synthetic organic chemistry and mechanistic studies

Beilstein Journal of Organic Chemistry ◽

10.3762/bjoc.13.221 ◽

2017 ◽

Vol 13 ◽

pp. 2235-2251 ◽

Cited By ~ 4

Author(s):

Grzegorz Mlostoń ◽

Heinz Heimgartner

Keyword(s):

Organic Chemistry ◽

Magnetic Properties ◽

Charge Transfer ◽

Reaction Mechanisms ◽

Building Blocks ◽

Charge Transfer Complexes ◽

Mechanistic Studies ◽

Oxidizing Agents ◽

Michael Acceptors ◽

Multistep Reactions

The scope of applications of dialkyl dicyanofumarates and maleates as highly functionalized electron-deficient dipolarophiles, dienophiles and Michael acceptors is summarized. The importance for the studies on reaction mechanisms of cycloadditions is demonstrated. Multistep reactions with 1,2-diamines and β-aminoalcohols leading to diverse five- and six-membered heterocycles are discussed. Applications of dialkyl dicyanofumarates as oxidizing agents in the syntheses of disulfides and diselenides are described. The reactions with metallocenes leading to charge-transfer complexes with magnetic properties are also presented.

Download Full-text

An enantioconvergent halogenophilic nucleophilic substitution (SN2X) reaction

Science ◽

10.1126/science.aau7797 ◽

2019 ◽

Vol 363 (6425) ◽

pp. 400-404 ◽

Cited By ~ 27

Author(s):

Xin Zhang ◽

Jingyun Ren ◽

Siu Min Tan ◽

Davin Tan ◽

Richmond Lee ◽

...

Keyword(s):

Organic Chemistry ◽

Nucleophilic Substitution ◽

Steric Hindrance ◽

Substitution Reaction ◽

Common Variant ◽

Nucleophilic Attack ◽

Mechanistic Studies ◽

Leaving Group

Bimolecular nucleophilic substitution (SN2) plays a central role in organic chemistry. In the conventionally accepted mechanism, the nucleophile displaces a carbon-bound leaving group X, often a halogen, by attacking the carbon face opposite the C–X bond. A less common variant, the halogenophilic SN2X reaction, involves initial nucleophilic attack of the X group from the front and as such is less sensitive to backside steric hindrance. Herein, we report an enantioconvergent substitution reaction of activated tertiary bromides by thiocarboxylates or azides that, on the basis of experimental and computational mechanistic studies, appears to proceed via the unusual SN2X pathway. The proposed electrophilic intermediates, benzoylsulfenyl bromide and bromine azide, were independently synthesized and shown to be effective.

Download Full-text