Science of Synthesis provides critical reviews of the organic and organometallic synthetic literature, with full-text descriptions of organic transformations and synthetic methods, experimental procedures, and citations back to the primary literature. The collection can be searched by text or chemical structure. This also includes access to the Houben-Weyl Methods of Organic Chemistry, covering the synthetic literature back to 1834. (Most of this series is in German, with some English volumes published in the 1980s and 1990s. The entire current Science of Synthesis collection is in English.)
For more information about using Science of Synthesis, Thieme has provided some case studies and teaching resources (including an index of name reactions with links to SoS content).