Silver-zeolite catalysed solvent free synthesis of (spiro)ketals

Easy, Green and Safe Carbonylation Reactions through Zeolite‐Catalyzed Carbon Monoxide Production from Formic Acid

“…It was thus tempting to use solid acids to produce CO from formic acid and to trap the gas formed in carbonylation reactions. In the present work, we took advantage of our expertise in zeolite‐induced chemistry14–17 to tune the exclusive formation of CO and to combine it with palladium‐catalyzed carbonylation reactions in a specifically designed but easy to set up and very cheap two‐reactor system.…”

[2,3] Sigmatropic Rearrangement of Propargylic Sulfinates by a Pale Ag1‐USY Zeolite and Silver Salts

“…[11c, 14] We found that the zeolites can also be used directly without preactivation between runs. We examined the recyclability of the zeolites and found that they can be used at least three times without any significant decrease in yield, but that reaction times increased with each successive reuse ( Table 3).…”

“…[13e, 14,15] Initially, we began with an examination of several solvents to determine the most efficient medium for the reaction. We believed that dichloromethane or nitroethane would be the best choice as per previous work [7b] and this turned out to be correct.…”

“…Less active catalysts were silver fluoride, nitrate, phosphate, acetate, and carbonate, which required longer times but still gave excellent yields of the allenic sulfone (Table 5, entries 6-10). Salts such as silver bromide, iodide, cyanide, and sulfate were ineffective at catalyzing the rearrangement in dichloromethane (Table 5, entries [11][12][13][14]. The five most reactive silver salts were reduced in catalyst loading to 2 mol% and subjected to a careful evaluation of the reaction time (Table 5, entries 15-19) The previously reported silver hexafluoroantimonate effected an essentially instantaneous reaction, followed very closely by silver tetrafluoroborate, trifluoromethanesulfonate, and perchlorate, all reactions being complete within 6 min.…”

“…The Ag 1 -USY was prepared by the Pale group as detailed in ref. [14] [17] The inital silver tetrafluoroborate sample that was used was deliquesced (Table 5, entries 2 and 16). The rearrangement proceeded very quickly and was complete in 2 min.…”