Ketone from acetals

The position of equilibrium is favorable for acetal formation from most aldehydes especially when excess alcohol is present as the reaction solvent For most ketones the position of equilibrium is unfavorable and other methods must be used for the prepara tion of acetals from ketones... 

The photochemical formation of ring-expanded acetals from ketones in alcoholic solvents was originally suggested by Yates and Kilmurry (9,38) to proceed by way of oxacarbenes (e.g., Scheme II) (39). The inter-... 

Reminder of chemistry from this chapter - making acetals from ketones is difficult - and drawing a mechanism related to, but different from, one in Problem 4. 

The ease of ring formation helped us to make five-membered cyclic acetals from ketones and a seven-membered heterocyclic compound (see Chapter 6). In this chapter we have seen how three-membered epoxides are formed. Ring formation is generally preferred to bimolecular reactions forming open chain compounds providing that the ring is three-, five-, six-, or seven-membered. Four-membered ring are a special case discussed in Chapter 29 where all these points are developed more fully. 

H2SO4 and ZnCl2 are better catalysts than HCl for the formation of diseleno-acetals from ketones, and Mel is useful in the conversion of such products into vinyl selenides. ... 

Mesitylmagnesium bromide Enol acetates from ketones Sterically hindered compounds... 

TBDMS triflate has been used in place of the more commonly employed TMS triflate as a catalyst in the Noyori protocol for the formation of cyclic acetals from ketones and l,2-his(trimethyl-siloxy)ethane (eq 16). ... 

If the alcohol is unhindered, a mixture of enol acetate (from ketone) and acetate results (eq 13). ... 

Acetylation of Other O, N, and C Centers. In addition to the preparation of enol acetates from ketones, isopropenyl acetate has also seen use in the acetylation of other O, N, and C centers. Hydroxy acetylation was first noted" as a simultaneous reaction... 

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