Asymmetric hetero-Diels–Alder reaction of chiral pinanediol 1,3-dienylboronates with azo-compounds

The asymmetric hetero-Diels–Alder reaction of 1,3-dienylboronates 1a and 1b with azo-compounds was investigated. The inductive effect of the methyl in 1,3-dienylboronate 1a resulted in an unusual product 7, while the normal cycloadduct 8 could be obtained as the single stereoisomer by using 1,3-dienylboronate 1b.