Maxwell James Parrott

Alkanes and Alkenes

In 1849 [1] Kolbe attempted to isolate the methyl radical via the electrolysis of an aqueous solution of potassium acetate. The hydrocarbon he obtained is now known to be ethane, but further investigations into the electrolysis of the alkali metal salts of aliphatic carboxylic acids have shown the reaction to have considerable utility for the synthesis of dimeric hydrocarbon products.

A new reagent for the mediation of amide bond formation in peptide synthesis

Abstract The potential application of 1-oxo-1-chlorophospholane (5) as a novel reagent for the in situ activation of Nα -protected amino acids for use in peptide bond forming reactions has been examined. Wherever possible, 32.4Mhz 31 P nuclear magnetic resonance (n.m.r.) spectroscopy was employed to follow both the formation of the intermediate phospholanic-carboxylic mixed anhydride and the subsequent aminolysis reaction.

The coordination chemistry of manganese. Part VI. [1–4]. Bis(tetrahydrofuran)manganese(II) halide complexes; synthesis and characterisation

Abstract The solid state structures of Mn(THF) 2 X 2 (THF = tetrahydrofuran; X = Cl, Br, I) appear to be halide-bridgedpseudooctahedral polymers which do not exhibit EPR signals. The EPR-active Mn(THF) 2 (NCS) 2 is a pseudotetrahedral monomer. In tetrahydrofuran solution the Mn(THF) 2 X 2 complexes react with PPhMe 2 to form a complex which can reversibly absorb/desorb molecular oxygen in a manner analogous to the authentic haem analogues Mn(PPhMe 2 )X 2 . However, reaction of Mn(THF) 2 X 2 with PPhMe 2 in acetonitrile, followed by exposure to dioxygen, results in rapid decomposition to an EPR-inactive species, presumably manganese(III), accompanied by production of some OPPhMe 2 . An authentic sample of Mn(PPhMe 2 )Br 2 in acetonitrile also undergoes similar decomposition on exposure to dioxygen. Polarographic and other characterisation data are reported for the Mn(THF) 2 X 2 complexes.

Perfluoro [2(e),6(e)-dimethylpiperidin-N-oxyl]

Abstract UV irradiation of solutions of perfluoro [ N -fluoro-2( e ),6( e )-dimethylpiperidine] ( 8 ) in the presence of oxygen and silica creates a persistent free radical with ESR spectroscopic parameters consistent with perfluoro [2( e ),6( e )-dimethylpiperidin- N -oxyl] ( 7 ). Attempts to isolate this new oxyl from products of preparative experiments in which the corresponding NON compound presumed to be formed initially had been thermolysed proved unsuccessful: only dilute solutions of the oxyl (ca. 1% yield) in (mainly) its NF precursor ( 8 ) were obtained.

Carboxylic Acids and Their Derivatives

Radical additions to unsaturated compounds are attractive methods for preparing carboxylic acids and their derivatives (ester, halide, lactone, amide, anhydride). The carboxylic acid function may be in the unsaturated compound, for example cyclopentanone adds to undecylenic acid affording a 70% yield of product [1].

Free Radical Reactions

In recent years many different reactions have been found to involve the intermediacy of free radicals. Such reactions, although diverse in nature, do have a number of common features. In a first stage radicals are usually produced by the thermal or photochemical fission of a covalent bond, or in a redox reaction. Less usual is radical formation by molecule-molecule interaction. In a second stage radicals may combine or disproportionate to give products, substitute for an atom or group in a neutral molecule, add to multiple bonds, fragment or rearrange. When, in successive stages a radical reacts with a substrate to produce a new radical, and this new radical reacts with the original radical source to afford a product, so regenerating the original radical, a chain reaction is set up. This continues until the chain is terminated by radicals being removed from the system. As an alternative to reaction with a substrate, free radicals can also afford products in oxidative processes. Because of the diversity of reaction that a radical may undergo, a number of different products usually results from a reaction involving free radicals. Due to the increase in knowledge of radical reactions (Organic Reaction Mechanisms covering the year 1975 surveys 1,100 papers on radical reactions [1]), and of how they are affected by change in reaction conditions, certain reactions have been developed to give one readily isolated product. Such reactions can often be useful in affording products that are not readily available by other means.

Ethers, Peroxides, and Hydroperoxides

The α-alkylation of ethers via the addition of alkoxyalkyl radicals to alkenes, although seemingly an attractive method for preparing more highly branched ethers, has received little attention. Apparently telomerisation is extensive and the product mixture is ill-defined [1, 2].

Sulfur-containing Compounds

The weak sulfur-sulfur bond in elemental sulfur allows carbon-centred radicals and thiyl radicals to effect Sh2 reactions at such sulfur atoms leading to the formation of poly sulfides. For example [1],

Naturally Ocurring and Related Compounds

Me_2 \dot CCN + S_8 \to Me_2 (CN)CS_n C(CN)Me_2