Synthetic Methods Database

Remember, however that CHAOS does not intend to be a database of "synthetic methods" presently available to organic chemists. CHAOS is aimed at finding the intermediate precursors of the "synthesis tree" by means of selected basic disconnections (either "consonant" or "dissonant"). In the author s view, it is of minor importance, for instance, how a "carbene" -resulting from a -(2 + 1) cycloelimination- is generated, or whether a double bond is the direct result of a Wittig reaction or the dehydration of an alcohol formed in a Grignard reaction. In... 

A subtle, but no less profound effect of this completely new approach is in the way chemists handle the vocabulary of their profession, a knowledge of possible chemical transformations. It could be said that it will become less important to memorise lists of synthetic methods, but this creates a problem. Computer reaction databases are only as good as the questions we ask them, and without a sound knowledge of what is chemically feasible, we cannot construct a query to obtain the exact reaction conditions we need. 

In addition a number of elecuonic databases are particularly useful for searching synthetic methods most notable amongst these being CASREACT and REACCS both of which allow access to a huge number of uansformations (see Section 17.3). 

A design module will provide the capability to select the compounds and the method by which they will be synthesized. In order to perform this task, the design module must be linked to external databases that can provide data about the availability of chemical reagents and information about synthetic methods. Once the products are selected and the synthetic method selected, this information will be collated in the reaction workbook. The function of the design module is complementary to diversity assessment tools. 

Beilstein Handbook of Organic Chemistry - The classic source of data on organic compounds, dating from the 18 century, Beilstein was converted to electronic form in the last decade of the 20" century. Over 8 million compounds and 5 million chemical reactions are now covered, with a broad range of physical properties as well as synthetic methods and ecolr cal data. The database is accessed by the CrossFire software... 

A reaction database-searching program. Available databases include Theilheimer (46,800 reactions). Journal of Synthetic Methods (35,800 reactions). Chiral Synthesis (11,300 reactions). Comprehensive Heterocyclic Chemistry (38,000 reactions) and others. 

An explicit reaction scheme is one that has been reported in the literature. Explicit schemes may or may not be indexed in a special way in the reaction database system. Approximately 15% of the reactions in Theilheimer s Synthetic Methods are reported as reaction schemes. In the ORAC Theilheimer database, each individual reaction step and the overall transformation is stored as a separate entry. For example, a sequence A—>C— D is indexed as the three reactions A->B, B->C and C D, plus the overall transformation A- D. A drawback of this approach is that transformations such as B D cannot be located in answering a... 

For an existing database containing few and/or short schemes, such as Theilheimer or The Journal of Synthetic Methods (JSM), this would represent an increase in the total number of reactions of about 20% over that for single-step reactions alone, and a negUgible increase over manual registration of summary reactions (the increase is due to the inclusion of some summary reactions that were not registered manually). The time required to execute a search will increase at the same rate, since REACCS RSS search time is generally hnear with the number of reactions. 

FIZ Chemie = Fachinformation.szentrum Cheniie ISl = institute for Scientific Information IRDAS = ISIS reaction database access system ISIS = integrated scientific information system JSM = Journal of Synthetic Methods MACCS = molecule access system MOS = Metlwd.s in Organic Synthesis, ORAC = Organic Reaction Acce.ss by Computer REACCS = Reaction Access System SMD = standard molecular data SPORE = Solid Phase Organic Reactions, STN = Scientific and Technical Information Network SYNLIB = Synthesis Library. 

Current awareness of new chemical reactions can. in principle. be organized in databases as for other types of queries, with search profiles that are automatically executed at each database update ( alerts . SDls ). Because of the frequency of updating (see Section 3.2), at present this only makes sense for CASREACT. Although the printed current awareness journals, such as the Journal of Synthetic Methods, Current Chemical Reactions, Methods in Organic Synthesis, and Cheminform RX are all available in electronic form, both as in-house databases for MDL s REACCS or ISIS system, and, with the exception of Current Chemical Reactions and Methods in... 

Theilheimer database is continued in time by JSM-REACCS. which contains 55 500 reactions (1980-199. ) and is increased by approximately 3000 reactions per year from 285 Journals and patents. In 1996. STN began to offer the Jourmil of Synthetic Methods online (but not Theilheimer) as DJS-MONLINE, with substructure. search facilities for reactants and products, including mapping and reaction centers (about 48000 reactions, 1975-1995). 

CCR contains 243000 reactions (1986-1994), and its annual growth is more than 30000 reactions, almost half of these being new synthetic methods. Sources for the database are about 350 Journals (before 1992, about 150) and US patents the printed CCR and the CD-ROM ChemPrep (see Section 3.2.11) are produced from only about 100 Journals. Besides the usual bibliographic information, full abstracts are also included in CCR (since 1991). Three of the 11 reactions from Goldsmith and Soria were retrieved from CCR. 

A subset of Chemlnform RX containing selected novel organic reactions and new synthetic methods is available (only in-house) as CSM (Current Synthetic Methodology FIZ Chemie REACCS or ISIS I992- twice annually) with an annual growth of about 7000 reactions. CSM relea.se 96.2 contained 34026 reactions (1992 to the first half of 1996). CSM contained only three of the eight examples (from Goldsmith and Soria ) from the full database Chemlnform RX. 

As quite a number of reactions are, like other chemical information, first, or only, published in patents, these are an important source of reaction information, even though one would normally assume that new synthetic methods would also be published in the journal literature. Since 1991, reactions taken from patents have been included in CASREACT patents comprise less than 10% of the CASREACT database in 1997, compared to about 16% of the CA database. CrossFire plus Reactions contains many reactions from patents registered before 1980, when Beilstein ceased to index patents. About 14% of the reactions in CRDS/JSM and 10% of those in ChemReact originate from patents CCR includes only US patents, which contribute about 10% of the reactions and Cheminform covers no patents at all. 

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