Homoallyl tandem acetalization-allylation

Tandem acetalization-allylation reaction of aldehydes with allylsilanes provides a convenient route to homoallyl ethers.82 Under catalysis by Sc(OTf)3, various aldehydes can be converted into homoallyl ethers by treatment with... 

The reaction of carbonyls with alcohols or TMS ethers under catalysis by (la) or Mes Sil provides an efficient, rapid access to oxocarbenium ions. The oxocarbenium ions generated in situ have frequently been utilized for the Hosomi-Sakurai allylation (Scheme 9.14) [2, 56]. This tandem acetalization-allylation reaction is quite convenient to the synthesis of homoallyl ethers. 

Very recently the tandem hydroformylation/acetalization has been used for the synthesis of new synthetically valuable chiral auxiliary derived from camphor. Stereoselective allylation of camphor and subsequent terminal hydroformylation of the resulting homoallylic alcohol affords the 5-lactol auxiliary (camTHP OH) in multigram scale (Scheme 8) [41]. 

In Scheme 13.17. decarboxylative Claisen rearrangement (dCr) reaction of myrtenyl tosylacetate 19 is shown. The sole product obtained for this tandem transformation was that of delivery of the ketene acetal to the allylic double bond in a sense anti to the more sterically demanding dimethyl-substituted methano bridge. Subsequent decarboxylation in situ gave the homoallylic sulfone 20. This reaction gave similar yields when carried out under microwave conditions. 

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