All You Need to Know About Asymmetric Phase Transfer Catalysis (PTC)

The subject of asymmetric PTC has moved on a lot since the early days in the 1980’s when the group of Dolling and Grabowski at Merck were pioneering the method on the scale up of manufacturing a drug substance. (Dolling U H et al, J Am Chem Soc, 1984, 106, 446; Hughes D L et al, J Org Chem, 1987, 52, 4745). Although the names of Corey in the US, and Lygo in the UK have been recently associated with asymmetric PTC, more recently it is the name Keiji Maruoka (Japan) who has published widely on the subject, and is becoming another key person in the field. Maruoka’s group has focussed on totally synthetic PTC’s rather than relying on alkaloid skeletons for their synthesis. The PTC’s catalyse a wide range of reactions. more>
• Trevor Laird

 

Any Old Iron? Any Ord Iron?

The reaction of Grignard reagents with alkyl halides is normally carried out with nickel catalysts (Kumada coupling). It has recently been shown by a number of groups in UK, France, Germany and Japan that iron catalysts can work well, but some workers have found that the results can depend on the quality of the iron, particularly when FeCl3 is used.
• Trevor Laird
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Safety and Selectivity in the Scale Up of Chemical Reactions

A NEW Course. The aim of the course is to give lab chemists an understanding of the issues that need to be considered during the early stages of scale up to large laboratory scale equipment (10-20 litre vessels)/kilo lab.
The course will concentrate on chemical safety and selectivity issues and include information on what safety testing equipment is available and the uses and limitations of this equipment. more>

Solvent Effects and Effect of Additives in the Asymmetric Reduction of a Key Statin Intermediate

Initial studies on the selective asymmetric hydrogenation of the carbonyl group of a key statin intermediate were complicated by byproduct formation.
It was eventually realized that the ruthenium BINAP catalysts have acidic properties which cause reactions with solvents (eg methanol and ethyl acetate) to occur. When 0.5 moles of triethylamine were added with methanol as solvent, a high syn/anti ratio of products was obtained and a quantitative conversion occurred in 100 minutes. If 1 mole of the amine was added, however, the reaction slowed and 2 moles caused the reaction to almost stop.
• Trevor Laird
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Direct Conversion of Carboxylic Acids to
Trifluoromethyl Ketones

A recent publication from workers at Boehringer-Ingelheim* describes a method for the direct conversion of primary and secondary carboxylic acids to trifluoromethyl ketones by reaction with trifluoroacetic anhydride (TFAA) and pyridine in toluene.
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Sodium Iodide as a Catalyst in C-C bond
Forming Reactions

1-bromo-1-nitroalkan-2-ols are used in the manufacture of photographic and ink-based materials, possibly because of their biocidal and antimicrobial properties. The existing methods for the synthesis of these molecules are low-yielding and this prompted workers at the University of Oviedo, Spain to investigate alternative, cheaper methods.
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Work Up of Borane Reductions of Amides and Imides

The initial product of the borane reduction of an amide or imide is not usually the desired amine, but the amine:borane complex. Cleaving these complexes can be problematic and if carried out with acids or inorganic bases hydrogen is liberated which creates potential fire and explosion hazards.
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Solvent Recovery Handbook

By Ian Smallwood

In a recent Topical Tip we referred to the ‘Solvent Recovery Handbook’ by Ian Smallwood as being essential reading. A number of copies are available to purchase from Dr Smallwood’s daughter. Please contact us if you would like more information.

• Trevor Laird

You know you've qworked in the lab too long when ......

 

... no matter what the timings in the experiment protocol there is always time for lunch in the middle!

 

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