Development of carbon-carbon bond-forming reactions via novel sulfur-containing reactive species

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It is one of the most important problems in synthetic organic chemistry to develop and discover new highly selective and efficient synthetic reactions. Functionalities such as carbonyl, alkenyl, and alkynyl groups have been widely utilized to develop new transformations of carbon-skeletons. On the other hand, the focus was laid on sulfur isologues of amides, i.e., thioamides. The generation of reactive species from thioamides and their application to carbon-carbon bondforming reactions were explored.・Carbon-carbon bond-forming reactions via sulfur-containing anionic speciesThe reaction of thioamides with two equivalents of BuLi proceeded smoothly at ℃ -rt to generate thioamide dianions. The ring opening of oxiranes with the thioamide dianions took place selectively at the carbon atom adjacent to the nitrogen atom of the dianions, followed by the hydrolytic workup to regenerate thiocarbonyl groups. This reaction was applied to a variety of oxiranes, and synthetic methods for 1,3-amino alcohols and oxazines, which are one of the most useful compounds, were provided.・Carbon-carbon bond-forming reactions via sulfur-containing cationic speciesMethylation of thioamides with MeOTf was complete within a few seconds to give thioiminium salts. Then, the addition of lithium acetylides and organomagnesium reagents to the obtained thioiminium salts was carried out. As a result, tertiary progaryl amines bearing new carbon skeletons were obtained with high efficiency and selectivity. Additionally, the addition of organozinc acetylides to the thioiminium salts leading to tertiary amines with enyne skeletons was also achieved.In summary, the species used in the studies are derived from the thioamides, which are readily prepared from commercially available materials. On the basis of the species new synthetic routes to valuable derivatives, which were not easy to be obtained by known methods, were established.