Pergamon Tetrahedron Letters 39 (1998) 9283-9286 TETRAHEDRON LETTERS Ytterbium Triflate Catalysed Allylation of Aldehydes: An Unusual Benzoic Acid Induced Acceleration Helen C. Aspinall, Nicholas Greeves* and Edward G. McIver Department of Chemistry, Donnan and Robert Robinson Laboratories, The University of Liverpool, Crown Street, Liverpool L69 7ZD, United Kingdom. Received 13 August 1998; accepted 1 October 1998 Abstract Addition of one equivalent of benzoic acid greatly enhances the efficiency of our ytterbium triflate catalyzed allylation of aldehydes with allyltributyltin in acetonitrile. Crucial modifications to reaction conditions result in a dramatically increased rate at remarkably low catalyst loading. © 1998 Elsevier Science Ltd. All rights reserved. Keywords" Lanthanides; Catalysis; Acidity; Tin and compounds Over recent years, lanthanide triflate mediated Lewis acid catalysis has attracted tremendous interest throughout scientific communities [1,2]. Their low toxicity, ease of handling, recyclable nature and low cost make lanthanide derived species attractive alternatives to their classical competitors such as TIC14, particularly in large-scale industrial processes. Allyltin and aUylsilicon reagents have been widely used for the mild conversion of aldehydes and ketones to versatile homoallylic alcohol intermediates. Whilst numerous Lewis acids promote these reactions, there has been little precedent for catalysis by lanthanide derivatives - which can potentially be recovered and reused. Aggarwal and co-workers have demonstrated that scandium triflate is capable of catalysing the allylation of aldehydes with allyltrimethylsilane [3]. We have previously reported that Yb(OTf)3 [4] and lanthanide triflate polyethethylene glycol complexes [5] catalyse analogous allylations with allyltributyltin in dichloromethane solvent. Although these novel procedures are very mild and versatile, there has been considerable scope for improvement: up to 10mol% of the catalyst is necessary, the reactions are rather sluggish, and require as long as 24 hours to reach completion. 0040-4039/98/$ - see front matter © 1998 Elsevier Science Ltd. All rights reserved. PII: S0040-4039(98)02086-3