A Review of U.S.Patents in the Field of Organic Process Development Published during March and April 2005

摘要

This review covers 20 patents from an original list of 239 that,it is hoped,will be of interest.One thing that struck me in this selection is that there are a number of patents in which mixing or changing the order of reagent addition appears to be central to the work.This could imply that chemists are becoming more aware of mixing or that engineers are becoming more involved in R&D.Whatever is the reason,it is refreshing to note that the chemistry and process engineering aspects are being viewed in parallel.The first patent on mixing is an aromatic nitration that uses static mixers to improve conventional nitration reactions,and changing the order of addition also reduces wastes.An improved method of making the disinfectant bronopol is based on changing the method of adding the reactants.This allows better control of the heat released in the highly exothermic process,and temperature control is key to obtaining high yields.An improvement in making the macrocyclic ketone civetone,without recourse to high dilution methods,also relies on mixing and changing the method of adding reagents.The addition of a corrosion inhibitor to a reaction mixture is probably not something normally considered,but this is what is done in an improved method of making a pesticide.The key reagent is trifluoro-peracetic acid,and this is highly corrosive to glass-lined reactors.However,it has been found that by adding boric acid to the reaction the rate of corrosion was reduced by a factor of 60.Clearly it is much cheaper and quicker to do this than to buy a new corrosion-resistant reactor.Naturally occurring or renewable materials continue to be of interest as sources of intermediates for drugs and other products.In one patent sugars are used to produce monomers used in polyester manufacturer.In a second patent the subject is taxols that are anti-cancer drugs that can be obtained from yew tree bark.The taxols are present in very low concentrations,and a simplified process of purifying them is described that does not require chromatographic equipment.Vitamin E and tocopherols are the subjects of two patents with one describing a method of isolating one isomer,with potential in treating prostate cancer,from vegetable oils.The second patent describes a process to prepare a range of intermediates suitable for vitamin E production.The use of highly active organometallic catalysts is of increasing importance in synthetic organic chemistry as well as in larger-scale production.One problem often overlooked is that high activity usually means high susceptibility to poisons and inhibitors.