Highly effective synthesis of 4-halo-tetrahydropyrans via a highly diastereoselective in situ Prins-type cyclization reaction

The reaction of aldehyde with homoallyl alcohols mediated by indium trichloride generated 4-chlorotetrahydropyrans in high yields and with high stereoselectivity. The same type of compounds can be generated through a single step, multi-component coupling between aldehyde and allyl bromide mediated by indium