The Hosomi–Sakurai reaction, also known simply as the Sakurai reaction, is an allylation reaction in which allyltrimethylsilane reacts with an electrophile under the catalysis of a strong Lewis acid. This reaction was jointly developed by Professors Hideki Sakurai and Akio Hosomi, and it bears their names. It is one of the important tools in organic synthesis.

• Reagents: Lewis acids

• Reactants: Allyltrimethylsilane, electrophiles (e.g., ketones, α,β-unsaturated aldehydes)

• Products: Allylic alcohols, amines, etc.

• Reaction Type: Addition reaction

Experimental Tips:

• Strong Lewis acids such as titanium tetrachloride (TiCl₄), boron trifluoride (BF₃), tin tetrachloride (SnCl₄), and diethylaluminum chloride (Et₂AlCl) are all effective in promoting the Hosomi–Sakurai reaction;

• The reaction is typically performed at temperatures between –78 °C and 25 °C, using dichloromethane (DCM) as the solvent, under an inert atmosphere such as nitrogen or argon;

• Common allylsilane reagents include allyltrimethylsilane and phenyl(dimethyl)allylsilane;

• Electrophilic partners can include aldehydes, ketones, imines, and α,β-unsaturated carbonyl compounds, yielding the corresponding alcohols or amines after the reaction;

• In some cases, allylchlorosilanes can be used in place of allyltrimethylsilanes.

Reaction Mechanism

Original Literature:

• Hideki Sakurai, Akira Hosomi, Makoto Kumada. J. Org. Chem., 1969, 34(6), 1764–1768.

Notable References:

• A Diosphenol-based strategy for the total synthesis of (−)-terpestacin, J. Am. Chem. Soc., 2007, 129, 4540.

• Enantioselective Aza–Sakurai Cyclizations: Dual Role of Thiourea as H-Bond Donor and Lewis Base, J. Am. Chem. Soc., 2016, 138, 14848.

• Scalable synthesis of bryostatin 1 and analogs, adjuvant leads against latent HIV, Science, 2017, 358, 218.