Allenylation reactions

In synthetic applications, Li et al. examined the propargylation-allenylation of carbonyl compounds by using a variety of metals including Sn, Zn, Bi, Cd, and In.203 By using the indium-mediated allenylation reaction, Li and co-workers developed the synthesis of the antiviral, antitumor compound (+)-goniofufurone (Scheme 8.22),204 a key component isolated from the Asian trees of the genus Goniothalamus,205 and other styryl lactone derivatives (Eq. 8.80). 

Cu(OH)2-catalyzed propargylation reaction was found to proceed rapidly and was completed within 5 min, even using 10 mol% of the catalyst to afford the desired product quantitatively (Table 5, entry 2). A lower loading (5 mol%) was also effective (Table 5, entry 3). On the other hand, the Bi(OH)3-catalyzed allenylation reaction was completed within 1.5 h in the presence of 5 mol% of... 

Thus, it was found that selective propargylation or allenylation reactions of hydrazonoester with allenyl pinacol boronate proceeded smoothly in the presence of a catalytic amount of bismuth(III) or copper(II) hydroxide in aqueous media. The use of metal hydroxide as a catalyst in organic synthesis is rare, and it is noteworthy that efficient catalysis occurred in aqueous media. In addition, the allenyl adduct was produced with high selectivity in the presence of Bi(OH)3, whereas the propargyl adduct was obtained with high selectivity in the presence of Cu(OH)2 as a catalyst. 

Wisniewska HM, Jarvo ER (2013) Enantioselective propargylation and allenylation reactions of ketones and imines. J Org Chem 78 11629—11636... 

Allenylation Reactions. The propargyltrimethylsilanes undergo Lewis acid-catalyzed reactions with electrophiles, with regiospecific rearrangement, to give substituted aUenes (eq 10). The catalysts usually employed are aluminum chloride, boron trifluoride etherate, and titanium(IV) chloride. 

Xia G, Yamamoto H. Catalytic enantioselective allenylation reactions of aldehydes with tethered bis(8-quinolinolato) (TBOx) chromium complex. J. Am. Chem. Soc. 2007 129 496 97. 

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