David J. Milner

Fluoroaromatics from Arylamines, a Convenient One-Pot Conversion Using Nitrosonium Tetrafluoroborate

Abstract A simple, novel and extremely versatile procedure has been identified for the conversion of arylamines into the corresponding arylfluorides. The amine is treated with nitrosonium tetrafluoroborate in dichloromethane and the resulting diazonium tetrafluoroborate is heated, without isolation or drying, to give the fluoromatic, generally in good yield. The method is applicable even to arylamines bearing carboxyl and hydroxyl substituents which give poor yields of arylfluorides under Balz-Schiemann conditions.

Asymmetric synthesis of cyclopropane carboxylates: Catalysis of diazoacetate reactions by copper(II) Schiff base complexes derived from α-amino acids

Abstract The asymmetric synthesis of cyclopropane carboxylates, which are intermediates in the synthesis of photostable pyrethroid insecticides, by catalysed reaction of ethyl diazoacetate with halo-olefins is described. Using chiral copper(II) Schiff base complexes derived from l -phenylalanine and aromatic aldehydes as catalysts, both the degree and direction of optical induction were found to depend upon the olefin. Unexpectedly, in several reactions there was marked stereoselectivity at C(3), rather than C(1), of the cyclopropanes. This novel pattern of selectivity is interpreted in terms of carbene transfer from a metal-carbene intermediate in which a chiral ligand controls the orientation of an approaching olefin.

Catalytic asymmetric synthesis of cyclopropane carboxylates: ligand—reagent interactions in diazoacetate reactions catalysed by copper (II) species bearing sugar—Schiff base ligands

Abstract The concept that ligand—reagent interactions might be useful in asymmetric catalysis has been used in designing copper (II) catalysts bearing Schiff base ligands derived from naturally occurring sugars. In reactions of ethyl diazoacetate with certain halogeno olefins, these catalysts have afforded precursors of photostable pyrethroids rich in the insecticidally important 1R cyclopropane isomers. In one case the cyclopropane carboxylate product contained 58% of the insecticidally most desirable cis-1R isomer. Less than 15% of this isomer is present in an equilibrium mixture of the carboxylates. The most stereoselective catalysts give the cyclopropane carboxylates in low yields, about 10%, based on ethyldiazoacetate used.

A Short and Economical Synthesis of 2,2,7,7-Tetramethyl-4-Octene -3,6-dione from 2-Furoic Acid and t-Butyl Chloride

Abstract 2,2,7,7-Tetramethyl-4-octene-3,6-dione (5), a useful synthetic intermediate, 1was required in kilogram quantities for further structural elaboration. Previous synthesis of (5) have given low yields 2 or have required unstable, 3 lachrymatory 4 or prohibitively expensive 5 intermediates. (5) has now been prepared in 43% overall yield by a route well suited to large scale operation (scheme)

The mono-alkyldecyanation of tetrafluoroterephthalonitrile by reaction with Grignard reagents

Abstract Treatment of tetrafluoroterephthalonitrile in THF with alkyl Grignard reagents gives the corresponding 4-alkyltetrafluorobenzonitrile in about 60% yield. The scope and limitations of this transformation are reported.

Conversion of acrylonitrile into 1,4-dicyanobuta-1,3-diene and propionitrile catalysed by group VIII metal species

Abstract At 150°C the conversion of acrylonitrile into nearly equimolar quantities of propionitrile and a mixture of 1,4-dicyanobuta-1,3-dienes is catalysed homogeneously by certain platinum and ruthenium species.

Conjugate addition of grignard reagents to para-substituted nitrobenzenes

Abstract Nitrobenzenes bearing masked aldehyde, ketone and ketoester functions at the 4-position undergo conjugate addition with Grignard reagents in THF at − 15°C. Sequential treatment of the 4-substituted nitrobenzenes with primary or secondary alkyl magnesium halides followed by 2,3-dichloro-5,6-dicyano-1,4-benzoquinone affords the corresponding 2-alkylated derivatives in 50–80% yields.

The beneficial effects of introducing sulphur substituents into hydroformylation substrates

Abstract Using RhH (CO) (PPh3)3 thioalkenes, in particular 2-vinylthiophene, PhSCHCH2 and 2-MeSC6H4CHCH2, are readily hydroformylated at 35°C with high regioselectivity (iso:n⩽19.5:1) and with no competing hydrogenation.

An Improved Procedure for the Synthesis of 3-Fluoroanthranilic Acid

Abstract 3-Fluoroanthranilic acid is derived in four steps from 3-nitrophthlic acid in 53% overall yield.

A Convenient Synthesis of Certain Hydroxymethyl Tetrahalogenobenzyl Bromides

Abstract Surprisingly, toluene solutions of certain tetrahalogenobenzene dimethanols rapidly afford the corresponding hydroxymethyl tetrahalogenobenzyl bromides in about 90% yield on treatment with hydrobromic acid without the need for continuous removal of the first formed product.