title: Oxidative Prins and Prins/Friedel-Crafts cyclizations for the stereoselective synthesis of dioxabicycles and hexahydro-1H-benzo[f]isochromenes via the benzylic C-H activation.
abstract: 1-Benzyl ethers of (E)- and (Z)-hex-3-en-1,6-diols and hept-3-en-1,7-diols undergo a smooth oxidative cyclization with DDQ in the presence of In(OTf)(3) through a sequential C-H bond activation and an intramolecular Prins cyclization to afford the corresponding trans- and cis-fused hexahydro-2H-furo[3,2-c]pyrans and octahydropyrano[4,3-b]pyrans respectively in good yields with an excellent stereoselectivity. Aryl tethered homoallylbenzyl ethers such as benzyl ethers of (E)- and (Z)-6-arylhex-3-enyl alcohols undergo a tandem Prins/Friedel-Crafts cyclization in the presence of stoichiometric amounts of DDQ and SnCl(4)via the benzylic C-H bond activation to furnish the corresponding trans- and cis-fused hexahydro-1H-benzo[f]isochromenes in good yields with complete stereoselectivity.
authors.affiliation: Division of Organic Chemistry-1, Indian Institute of Chemical Technology, Uppal Road, Tarnaka, Hyderabad 500670, India. basireddy@iict.res.in
authors.forename: B V Subba
authors.initials: BV
authors.lastname: Reddy
authors.forename: Prashant
authors.initials: P
authors.lastname: Borkar
authors.forename: J S
authors.initials: JS
authors.lastname: Yadav
authors.forename: P Purushotham
authors.initials: PP
authors.lastname: Reddy
authors.forename: A C
authors.initials: AC
authors.lastname: Kunwar
authors.forename: B
authors.initials: B
authors.lastname: Sridhar
authors.forename: René
authors.initials: R
authors.lastname: Grée