AHMED, A., CHRISTIE, S.D.R. and PRITCHARD, G.J., 2017. A comparison of the benzylic and the allylic group as a donor in the formal [4+2] cycloaddition to tetrahydropyrans using donor-acceptor cyclobutanes. Tetrahedron Letters, 58 (31), pp. 3028-3031.
The allyl group was shown to be preferred over the benzyl group as a donor in the formal [4+2]-cycloaddition reaction between a donor-acceptor cyclobutane and various aldehydes to give tetrahydropyrans.