[3+n] Annulation reactions by means of 3-(trimethylstannyl)-2-[(trimethylstannyl)methyl]propene, an isobutene dianion synthetic equivalent

Stepwise functionalization of the 2 C-Sn bonds in H2C:C(CH2SnMe3)2 (I) with electrophiles, diacyl dichlorides, or aldehydes and CO2 provides a promising route for annulation reactions. Thus, I reacted with H2C(COCl)2 in THF to give 93% orcinol. Reaction of I with RCHO [R = Ph, n-hexyl, (E)-PhCH:CH], followed by lithiation with BuLi, carboxylation with CO2 and acidic hydrolysis gave 45-65% unsatd. lactones II.