Hydrogenation of β-Keto Sulfones to β-Hydroxy Sulfones with Alkyl Aluminum Compounds: Structure of Intermediate Hydroalumination Products

β-Hydroxy sulfones are important in organic synthesis. The simplest method of β-hydroxy sulfones synthesis is the hydrogenation of β-keto sulfones. Herein, we report the reducing properties of alkyl aluminum compounds R(3)Al (R = Et, i-Bu, n-Bu, t-Bu and n-Hex); i-Bu(2)AlH; Et(2)AlCl and EtAlCl(2) in the hydrogenation of β-keto sulfones. The compounds i-Bu(2)AlH, i-Bu(3)Al and Et(3)Al are the at best reducing agents of β-keto sulfones to β-hydroxy sulfones. In reactions of β-keto sulfones with aluminum trialkyls, hydroalumination products with β-hydroxy sulfone ligands [R(2)AlOC(C(6)H(5))CH(2)S(O)(2)(p-R(1)C(6)H(4)](n) [where n = 1,2; 2aa: R = i-Bu, R(1) = CH(3); 2ab: R = i-Bu, R(1) = Cl; 2ba: R = Et, R(1) = CH(3); 2bb: R = Et, R(1) = Cl] and {[Et(2)AlOC(C(6)H(5))CH(2)S(O)(2)(p-ClC(6)H(4)]∙Et(3)Al}(n) 3bb were obtained. These complexes in the solid state have a dimeric structure, while in solutions, they appear as equilibrium monomer–dimer mixtures. The hydrolysis of both the isolated 2aa, 2ab, 2ba, 2bb and 3bb and the postreaction mixtures quantitatively leads to pure racemic β-hydroxy sulfones. Hydroalumination reaction of β-keto sulfones with alkyl aluminum compounds and subsequent hydrolysis of the complexes is a simple and very efficient method of β-hydroxy sulfones synthesis.