Binolam-AlCl: a two-centre catalyst for the synthesis of enantioenriched cyanohydrin O-phosphates.
The enantioselective synthesis of cyanohydrin O-phosphates by using in situ generated bifunctional catalysts (R)- or (S)-3,3'-bis(diethylaminomethyl)-1,1'-binaphthol-aluminium chloride (binolam-AlCl) is reported. The reaction, which can be described as an overall cyano-O-phosphorylation of aldehydes, has a wide scope and applicability. Evidence is also provided, including ab initio and DFT calculations, in support of supported by the Lewis acid/Brønsted base (LABB) dual role of the catalyst in inducing first the key enantioselective hydrocyanation, which is then followed by O-phosphorylation. A brief screening of the synthetic usefulness of the resulting cyanohydrin O-phosphates unveiles some interesting applications. Among them, chemoselective hydrolysis, reduction and palladium-catalysed nucleophilic allyl substitution, thereby leading to enantiomerically enriched alpha-O-phosphorylated alpha-hydroxy esters, beta-amino alcohols and gamma-cyanoallyl alcohols, respectively. Naturally occurring (-)-tembamide and (-)-aegeline are synthesised accordingly.
Baeza
Alejandro
A
Departamento de Química Orgánica, Facultad de Ciencias and Instituto de Síntesis Orgánica (ISO), Universidad de Alicante, Apdo. 99, 03080 Alicante, Spain.
Nájera
Carmen
C
Sansano
José M
JM
Saá
José M
JM