Synthesis of 5-Metalla-Spiro[4.5]Heterodecenes by [1,4]-Cycloaddition Reaction of Group 13 Diyls with 1,2-Diketones

Monovalent group 13 diyls are versatile reagents in oxidative addition reactions. We report here [1,4]-cycloaddition reactions of β-diketiminate-substituted diyls LM (M = Al, Ga, In, Tl; L = HC[C(Me)NDipp]2, Dipp = 2,6-iPr2C6H3) with various 1,2-diketones to give 5-metalla-spiro[4.5]heterodecenes 1, 4–6, and 8–10, respectively. In contrast, the reaction of LTl with acenaphthenequinone gave the [2,3]-cycloaddition product 7, with Tl remaining in the +1 oxidation state. Compound 1 also reacted with a second equivalent of butanedione as well as with benzaldehyde in aldol-type addition reactions to the corresponding α,β-hydroxyketones 2 and 3, while a reductive activation of a benzene ring was observed in the reaction of benzil with two equivalents of LAl to give the 1,4-aluminacyclohex-2,4-dien 12. In addition, the reaction of L’BCl2 (L = HC[C(Me)NC6F5]2) with one equivalent of benzil in the presence of KC8 gave the corresponding 5-bora-spiro[4.5]heterodecene 13, whereas the hydroboration reaction of butanedione with L’BH2 (14), which was obtained from the reaction of L’BCl2 with L-selectride, failed to give the saturated 5-bora-spiro[4.5]heterodecane.