The cross-coupling reaction between halocarbonyl compounds with Knochel's (dialkoxyboryl)methylzinc reagent provided a new synthesis of oxoalk-2-enylboronates; the in situ cyclization of these boronates gave 3-methylene cyclopentanols or cycloheptanols in high yields.
A catalytic asymmetric synthesis of the α-methylene lactones starting with the prochiral alkenyl halides 8 and 19 has been achieved for the first time, giving 9 in 57% enantiomeric excess (e.e.) and 20 in 39% e. e., respectively.