Molecules 2000, Chemia, biochemia, Molecules

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//-->Molecules2000,5,1-3moleculesISSN 1420-3049EditorialMolecules, MolBank and ECSOC-4Reinhard Neier, Editor-in-ChiefInstitut de Chimie, Av. Bellevaux 51, CH-2000 Neuchâtel, SwitzerlandTel.: +41 32 718 2428, Fax: +41 32 715 2511, E-mail: reinhard.neier@ich.unine.ch,Received: 18 January 2000 / Published: 19 January 2000It is one of the great ironies of our information age that at the same time that we have the technicalcapability to make information freely available world-wide, budget problems are seriously endanger-ing the free access to scientific information. The crisis of our science libraries has unfortunately inten-sified with the availability of access to many of the traditional journals via the Web. Ironically, evenlearned societies often demand considerably more for a license for the Web version of their journalsthan for the paper subscription alone. In contrast to the initial optimistic predictions by some prophetsof the Internet, the budget situation of our libraries has become worse as they are faced by seemingendless price increases, and many academic science departments and even huge companies are rou-tinely forced to reduce the number of their subscriptions to journals. At the same time, the number ofnovel compounds synthesized by chemists or identified from an isolation procedure increases expo-nentially. Finally, it has become clear that libraries of molecules will be an important tool for solvingthe challenges of the future and for finding the molecular solution to many of the problems of our soci-ety.As an answer to many of these challenges Dr. Shu-Kun Lin from MDPI launchedMolecules(ISSNthe chemical community at large by publishing full experimental and spectroscopic data of newlysynthesized compounds. Three major goals were pursued:qThe experimental data should become fully available without the usual restriction ap-plied in many traditional chemical journals (small print, highly condensed versions, re-Molecules2000,5porting of only selected data or in the communication format, even suppressing the ex-perimental part completely).q2The journal should strive to fully use the enormous potential of the World-Wide Weband thereby provide access to this valuable data to scientists from all over the world.At the same time, the electronic journal should encourage the preservation of samples ofthe reported compounds. As methods to identify compounds and their properties becomemore and more sophisticated the preservation of a collection of compounds and theiravailability has become an important factor.qIn 1998 Dr. Esteban Pombo-Villar helped to increase the visibility of the electronic journal espe-cially by promoting the format of the electronic conferences (ECSOC-2 to ECSOC-3), and took overresponsibility forMoleculesas Editor in Chief during 1999. In a period when things are changing soquickly, the survival for five years of a journal of a completely new format without the financialbacking of either a learned society or of a big publishing house, must be viewed as a success story. Thesuccess ofMoleculesis even more impressive in view of all the odds that were against it. Thanks to theintensive personal efforts of Dr. Shu-Kun Lin and Dr. Esteban Pombo-Villar,Moleculeshas juststarted its fifth year in good health. We have to thank them for their tremendous efforts promotingelectronic publishing in chemistry.In view of his many other responsibilities Dr. Esteban Pombo-Villar has now asked to be replacedas Editor-in-Chief, but we are glad he will continue to supportMoleculesas a member of the EditorialAdvisory Board. Starting January the1st,I have accepted to act as Editor-in-Chief ofMolecules.To-gether with Dr. Derek J. McPhee, Dr. Luc Patiny, Dr. Andrey V. Gutnov and Dr. Shu-Kun Lin wehope as a team to remain true to the principles which helped to launch and to establishMoleculesandto help them flourish. Dr. Thomas Wirth has agreed to take over the responsibility for the planned EC-SOC-4 meeting and we are looking forward to an excellent collaboration in the hope of promoting ourscience.AsMoleculesis becoming bigger the editorial procedure and the refereeing will have to take fulladvantage of the possibilities of electronic handling of manuscripts. It is also clear to all of us that thefuture ofMoleculeswill depend very much on the very successful unique concepts of the preservationof compounds and the concept of demanding the full experimental description of reported compounds.As useful as these concepts are,Moleculeswants to be more than just an extensive database of newcompounds. In order to achieve this goalMoleculesneeds the collaboration of all scientists. It is ourhope to attract as many scientists as possible to submit their results toMolecules,taking advantage ofthe speed of electronic publication and the other possibilities offered by the electronic media to show-case their scientific contributions. It is also obvious that in doing this, we will not compromise the ac-cepted norms of the peer review system.Molecules2000,53In accordance with Dr. Esteban Pombo-Villar’s plans, we have decided to make a clear distinctionbetween reports on the synthesis of known or previously unknown compounds, which authors shouldMoleculesas shortnotes, and manuscripts describing a significant advance in science, which qualify for publication asfull papers inMolecules.We hope thatMolecules,MolBank and ECSOC-4 will keep ahead of the astonishing pace of devel-opments in the field of science publishing. We, from the Virtual Editorial Office, will try to makeMoleculesas attractive as possible for you. Please help us, be it as author of a manuscript, as a scientistcontributing short notes to the MolBank section, as a chemist participating in the upcoming electronicconference ECSOC-4 or be it as a referee of your peer’s work. Science and scientific journals can onlysurvive if a significant number of you are willing to collaborate and to develop the new methods ofelectronic publishing. Let us not just complain about the inevitable increase subscription prices of ourjournals, let us do something about it.Best wishes for the year 2000!Molecules2000,5,4-18moleculesISSN 1420-3049Recent Developments in the Area of Asymmetric TransferHydrogenationMartin Willsa,*,Matthew Palmera, Athene Smitha, Jennifer Kennyaand Tim WalsgrovebDepartment of Chemistry, University of Warwick, Coventry, CV4 7AL, UKTel.: (024) 7652 3260, Fax: (024) 7652 4112, E-mail: M.Wills@warwick.ac.ukbSmithKline Beecham Pharmaceuticals, Old Powder Mills, Nr Leigh, Tonbridge, Kent, TN11 9AN,UK*Author to whom correspondence should be addressed.Received: 14 September 1999 / Accepted: 15 November 1999 / Published: 21 January 2000aAbstract:The use of an enantiomerically pure amino alcohol, coupled to a transfer hydro-genation process, in the asymmetric catalysis of the reduction of ketones to alcohols, is de-scribed. The process works well for unfunctionalised ketones, affording e.e.s of up to 98%,and excellent conversions. We have recently extended, for the first time in this application,the scope of the methodology to the reductions ofα-heteroatomsubstituted substrates,through the use of the appropriate protecting groups on each atom.Keywords:asymmetric, transfer, hydrogenation, catalysis, ruthenium.IntroductionThe asymmetric reduction of ketones to enantiomerically enriched alcohols remains a pivotal trans-formation in organic synthesis [1,2]. Of the methods available to achieve this reaction in a catalyticsense the most established are those based on either hydrogenation [3-7] or the use of oxazaboroli-dines for the catalysis of ketone reduction by borane [8,9].Catalytic hydrogenation using a homochiral phosphine in conjunction with an appropriate metal,usually rhodium or ruthenium, is a versatile method which requires only very low levels of catalyst. InMolecules2000,55general, however, the method is most suitable for ketones which bear a proximal co-ordinating group[3-7]. There are however a number of recent notable examples of reductions of simple ketonesthrough the use of additives [10-13] and a remarkable system for the asymmetric hydrogenation ofsimple ketones using a combination of a Rh(I) complex of a chiral phosphine with lutidine and KBr asadditives has been reported very recently [14].The oxazaborolidine-catalysed borane reduction process is complementary to hydrogenation and isideally suited to the reduction of unfunctionalised ketones and enones [8,9]. The drawback of thismethod is the requirement for a relatively large quantity (usually at least 10 mol%) of catalyst and thenon-compatibility of certain functional groups with borane.In this paper the combination of a homochiral amino alcohol with ruthenium(II) is demonstrated toform an effective new system for the asymmetric catalysis of the transfer of hydrogen from isopropa-nol to acetophenone.Transfer Hydrogenation of KetonesAsymmetric transfer hydrogenation with Ru(II) complexes, in which we have recently commenceda programme of research, has recently emerged as an effective approach to asymmetric carbonyl re-duction [15].A particular advantage of transfer hydrogenation methodology is the requirement for only very lowquantities of catalysts; typically less than 1 mol%. Furthermore the ligands employed are often are in-definitely stable to the reaction conditions and may be recovered after use.We have recently discovered that (1R,2S)-(+)-1 is an excellent ligand for asymmetric transfer hy-drogenation of ketones (Scheme 1) [16]. The use of 1 mol% of1in conjunction with 0.25 mol% of theruthenium complex [RuCl2(p-cymene)]2and 2.5 mol% of KOH in propan-2-ol ([ketone]=0.1M) atroom temperature resulted in reduction of acetophenone to S-(-)-1-phenethanol in 70% isolated yieldand 91% e.e. after 90 minutes. Of a series of aromatic groups in the catalyst, p-cymene proved to besuperior to benzene and 1,3,5-trimethylbenzene. The reaction does not require exclusion of water orair and may be worked up simply by filtration of the reaction mixture through a plug of silica followedby removal of solvent.1 mol%O(1R,2S)-1PhMeNH2OHH OH72% isolated yield91% enantiomeric excesso(49% yield, 93% e.e. at 0C)PhMe0.25 mol% [RuCl(p-cymene)]2S22.5 mol% KOH, i-PrOH solvent, 4 hrsroom temperatureScheme 1.Asymmetric transfer hydrogenation of acetophenone using (1R,2S)-1.The presence of a primary amine function on the ligand appears to be crucial; use of the methylatedamine gave a product of only 20% e.e. In order to determine the importance of the rigid structure of the [ Pobierz całość w formacie PDF ]

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