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DOI: 10.1055/sos-SD-047-00100

Petasis, N. A.Science of Synthesis, (201047185.

The use of the Petasis reagent 37 is often the preferred method for the methylenation of esters to yield enol ethers due to its nonbasic and nonacidic nature and the simplified workup that avoids product decomposition. This methylenation process works well for a wide range of ester derivatives (Table 10),[‌60‌,‌64‌,‌72‌,‌85‌‌87‌] and further information can be found in Science of Synthesis, Vol. 32 [XEneX (X=F, Cl, Br, I, O, S, Se, Te, N, P), EneHal, and EneO Compounds (Section]. Methylenation of esters (Table 10, entry 1)[‌60‌] and α,β-unsaturated esters (entries 2 and 3)[‌64‌,‌85‌] gives the corresponding diene derivatives, while alkynoate esters also undergo reaction (entry 4).[‌64‌] Selective methylenation at the least hindered carbonyl group of a diester (entry 5) has been observed to proceed under microwave irradiation.[‌72‌] The methylenation of esters containing alkenyl groups works well (entries 6 and 7),[‌86‌,‌87‌] with the enol ether products obtained being used in subsequent cyclization reactions. The selective methylenation of a carbonyl group in an acetoxy substituent of a carbohydrate gives the corresponding isopropenyloxy-substituted carbohydrate (entry 8),[‌88‌] which has been used in the exploration of selective glycosylation reactions after hydrolysis of the pivaloyl residues.[‌88‌]

Meeee 88 Meeeeeeeeeeee ee Meeeee[‌88‌,‌88‌,‌88‌,‌88‌‌88‌]

Meeee Meeeeeee Meeeeeee Meeeeeeeee Meeeeee Meeee (%) Mee
8 Me(Me)8(Me)8 (88), eeeeeee, 88°M 88 [‌88‌]
8 Me(Me)8(Me)8 (88), MMM, 88°M 88 [‌88‌]
8 Me(Me)8(Me)8 (88), eeeeeee, 88°M 88 [‌88‌]
8 Me(Me)8(Me)8 (88), MMM, 88°M 88 [‌88‌]
8 Me(Me)8(Me)8 (88), MMM, eeeeeee, eeeeeeeee (888M), 888°M, 8e 88 [‌88‌]
8 Me(Me)8(Me)8 (88), eeeeeee, 88°M 88 [‌88‌]
8 Me(Me)8(Me)8 (88), MMM, 88°M 88 [‌88‌]
8 Me(Me)8(Me)8 (88), eeeeeee, 88°M 88 [‌88‌]

Mee eeeeeeeeeeeee ee eeeeee eeee eee Meeeeee eeeeeee 88 ee eeeeeeee eee eeeeeeeeee eeee eeee eeee-eeeeee eeee eeeeee, eeeee eee eeeeeeeeeee ee eeeeeeeeee eeeeeeeeeeeeee, eeeeeeeeeeee, eee eeeee eeeeeeeeeeeeeee (Meeeee 88).[‌88‌‌88‌] Meeeeeeeeeeee ee eeeeeee 88 eeeeeeee eeee eeeeeeeeee ee eeee Meeeeee eeeeeeeeeeeee ee eee eeee eeeee 88 ee eeee eee eeeeee 88. Meee eeeeee eeeeeeeeeeee eeeeeeeee e eeeeeee eeeeeeeeeeeee ee eeee eee eeeeee 88.[‌88‌] Meeee 88 ee eeeeeeeeeeee ee eeee eee eeeeeee eeeeee 88, eeeee ee eeeeeeeeeeee eeeeeeeeee eeeee Meeee eeee eeeeeeeee ee eeee eee eeeeee 88.[‌88‌] Meeeeeeee eee(eeeeeeeeeeeee) ee eeeeeeee 88 ee eee eeeee eeeeeeee eeeeeee eee eeeeee eeeee eeeeeeee eeeeee eeeee eee eee(eeee eeeee) 88, eeeee, eeee eeeeeee, eeeee eee eeeeeeeeeee eeeee 88 ee eeeeeeeeeeeee.[‌88‌] Meeeeeeee-eeeeeeee eeeeeeeeeeeee ee eee β-eeeee eeee eeeee eeeeeeeeee 88 eeeee eee eeee eeeee 88, eeeee eee eeee ee eeeeeeeee eeee eee eeeeeeeee-8-eee 88.[‌88‌]

Meeeee 88 Meeeeeeeeeeee ee Meeeee eeee eee Meeeeee Meeeeee Meeeeeee ee Meeeeeeeeeeee[‌88‌‌88‌]

Meeeeeeeeeee Meeeeeeee

(8M)-8-(8-{[(8M,8M)-8-Meeeeeeeee-8-ee-8-ee]eee}eeeee)-8-eeeeee-8,8-eeeeeeeee (Meeee 88, Meeee 8); Meeeeee Meeeeeeee:[‌88‌]

MMMMMMM: Meee eeeeeee ee eeeee ee eeeeeeeeeeee ee eee ee 88 °M, ee eee eeeee eeee eee Meeeeee eeeeeee eeeeeeeee e eeeee, eeeeeeeeee, eeeeeeeeeeeee eeeeeeeeeeeee eeee eeeeeeeee eeeeeee eee, eeeeeeeee ee e eeeee eeeeeeee ee eeeeeeee.

M eeee ee eee eeeeeeeee eeeee (888ee, 8.88eeee) eee eee Meeeeee eeeeeee 88 (888ee, 8.88eeee) ee eeeeeee (8.8eM) eee eeeeeee eeeeeeeee ee 88°M eeeee eeeee. Meeee eeeeeee ee ee, eee eeeeeee eee eeeeeee eeee eeeeeeeee eeeee (88eM) eee eeee eeeeeeee eeeeeee e eee ee Meeeee. Mee eeeeeeee eee eeeeeeeeeeee eee eee eeeeeee eee eeeeeeee ee eeeeee eeeeeeeeeeeeee ee eeeeee e eeeeeeeee eee; eeeee: 888ee (88%).

Meeeeeeeeee 8,8,8,8-Meeeeeee-M-eeeeeeee-α-M-eeeeeeeeeeeeeee (Meeee 88, Meeee 8); Meeeeee Meeeeeeee:[‌88‌]

M 8.8M eeee ee eee Meeeeee eeeeeee 88 ee eeeeeee (88eM, 88eeee) eee eeeee ee eee eeeeeeeee eeeeeee (8.88e, 8.8eeee). Mee eeeeeee eee eeeeeeeee eeee eeeee eee eeeeee ee 88°M eee 88e. Mee eeeeee eeee eee eeeeeee eeee eeeeeeeee eeeee eee eeeeeeee, eee eee eeeeeee eee eeeeeee eeeee eeeeeee eeeeeeee. Meeeeeeeeeeeee ee eee eeeeee eeeeeee (eeeeee eee, eeeeeee/eeeeeeeee eeeee 8:88) eeeeeeee eee eeeeeee; eeeee: 8.88e (88%).