Organochromium Reagents

This chapter describes carbon-carbon bond formation mediated by organochromium compounds, especially nucleophilic addition of the organochromiums to carbonyl compounds. The chapter covers the major advances in this field after the publication of the first edition of Comprehensive Organic Synthesys (ORS1) in 1991, and consists of three sections: (1) Formation of carbon-carbon single bond with allyl-, propargyl-, alkenyl-, aryl-, and alkynylchromium compounds: These compounds are prepared by reduction of the corresponding halides with chromium(II), and the latter three compounds requires to conduct under nickel catalysis. The carbonyl addition proceed under mild conditions in a regio-, stereo-, and chemoselective manner. (2) Formation of carbon-carbon double bonds with geminal dichromium reagents: The reagents are generated from geminal haloalkanes and chromium(II), and add to aldehydes to give E-alkenes stereoselectively. The reaction also proceed under mild conditions chemoselectively. (3) Miscellaneous carbon-carbon bond formation with other organochromium compounds. Examples of the organochromium reagents for natural product syntheses are shown in each section.