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

Phase-transfer catalysis (PTC) offers some advantages for scale-up, using cheap bases such as sodium hydroxide and the ability to re-use the catalyst, along with ease of product separation in most cases. Asymmetric PTC has been examined for the last 20 years or so, and catalysts are available from Sigma-Aldrich for procedures developed by the major academic groups in this field (Corey, Lygo, O’Donnell, Maruoka). more>
• Trevor Laird

 

Any Old Iron? Any Old Iron?

following on from Issue 21

Most chemists automatically turn to expensive palladium catalysts when faced with a cross coupling reaction, but removal of palladium residues from the product can be a major issue for large scale processes. A number of academic groups have recently published cross-coupling procedures using iron catalysts, of Grignard reagents with alkyl halides, and these look to have great potential for scale-up, as well as being more environmentally friendly. more>
• Trevor Laird

 

An Old But Useful Reaction

The Reformatsky reaction, introduced in 1887, has often caused problems for process chemists, partly due to its heterogeneous nature and dependence on the quality and surface properties of the zinc used. Now both homogeneous and heterogeneous versions exist, some using only catalytic quantities of activated metal. The reaction can often be used industrially and can be an excellent way to introduce two new centres in a diastereoselective manner. more>

More Robust and Reliable Cyanation Reactions

A recent publication from workers at GSK* concerns the palladium catalysed cyanation of aromatic halides with zinc cyanide. This reaction is very sensitive to traces of oxygen, which can cause catalyst poisoning. The resulting reactions can be difficult to restart. The group at RTP have found that the addition of 1 wt% of polymethylhydrosiloxane (PMHS) to the reaction mixture avoids the problem and allows reactions to progress even when fully exposed to the atmosphere. View the complete tip and diagram here

• Will Watson

Use of Hydrogen to Reduce Esters

Reduction of carboxylic acid esters to alcohols is usually achieved using stoichiometric amounts of hydride reducing agents, reactions which can be hazardous to scale. Work-ups on scale are often problematical and require great attention to detail. Now, chemists at the flavour/fragrance company Firmenich, in Switzerland have found a way to use hydrogen, using homogeneous ruthenium catalysts (Saudan L A et al, Angew Chem Int Ed, 2007, 46, 7473). more>

The Bohlmann-Rahtz Pyridine Synthesis

I must admit that I hadn’t heard of this particular named reaction, but it turns out to be a particularly flexible synthesis of pyridines. Fortunately, the group of Mark Bagley at Cardiff, UK has reviewed the reaction and this review summarises their own work as well as the work of others (SynLett, 2007, (16), 2459-2482). They cover important issues for process chemists such as choice of catalyst and solvent effects.
more>

Fine Chemicals - The Industry and the Business

By Peter Pollack

The fine chemicals industry, according to the author Peter Pollak, is worth $75 billion production value, some of which is for captive use, leaving an estimated $45-50 billion worth of potential business for the fine chemical industry. Despite the importance of the industry, there have been hardly any books, which have tried to describe what the industry is and how it functions.
From the list of subjects covered, it is clear that he has undertaken a mammoth task to describe a complex industry in under 250 pages. Inevitably some areas have received minimal discussion, possibly since he has based most of his views from his 30 years experience with Lonza, but he has made a brave and largely successful attempt to cover such a broad topic in a unique approach, and in a style which is readable yet often full of useful numerical data.
Although the text is littered with typos and not enough references, the book can be recommended to all those working in the fine chemicals industry and should be compulsory reading for newcomers to the fine chemical industry.

 

Handbook of Homogeneous Hydrogenation
(3 vols.)

By Johannes de Vries & Connelius Elsevier

With 45 chapters and 1568 pages, this is quite simply an ‘all you need to know about homogeneous hydrogenation’ set of books!

• Trevor Laird

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

 

... the Christmas night out reveals scientists can’t dance, although a formula for the movement of hands and feet combined with beats per min is found scrawled on a napkin by a waiter the next day!

“Process chemists are like postmen (mailmen), nobody takes any notice of us until we don’t deliver.” Alan Pettman, Pfizer

 

Share your useful, novel or new methodologywith our global community (12,000+ readers), email us your snippet and it could feature in future newsletters!

 

Your friends at Scientific Update would like to take this opportunity to wish you all a very Merry Christmas and Happy New Year!