Science of Synthesis

Petasis, N. A., Science of Synthesis, (2010) 47, 212.

The gem-dimetallic species formed by reacting diiodomethane with activated zinc [CH2(ZnI)2; see also ‌Scheme 27‌, compound ‌109‌ (X = I), Section ‌47.1.1.4.4‌] was amongst the first gem-dimetallic species shown to methylenate carbonyl compounds, and several efficient procedures have been developed for this process (‌Table 18‌).[‌150‌,‌151‌,‌153‌–‌157‌,‌178‌,‌179‌] The addition of trimethylaluminum is useful for the methylenation of aldehydes, including unsaturated aldehydes (‌Table 18‌, entry 1),[‌150‌,‌151‌] and ketones. In fact, these conditions can be used for the selective methylenation of an aldehyde in the presence of a ketone (entry 2).[‌153‌] This chemoselectivity can also be achieved using titanium(IV) isopropoxide as an additive (entry 3).[‌153‌] The combination of diiodomethane/zinc/titanium(IV) chloride, known as the Takai–Nozaki reagent,[‌154‌] is useful for the methylenation of readily enolizable ketones (entries 4 and 5).[‌154‌] It has also been used in the methylenation of a functionalized cyclobutanone (entry 6)[‌178‌] and a tetrahydro-4H-pyran-4-one (entry 7).[‌179‌] The use of the preformed gem-dimetallic species [CH2(ZnI)2] in combination with low-valent titanium (β-TiCl3 or TiCl2) is effective for the methylenation of ketones, even in the presence of esters (entries 8 and 9),[‌155‌,‌158‌] while the addition of N,N,N′,N′-tetramethylethylenediamine enables the methylenation of esters (entry 10).[‌156‌] For ketones having α-oxygen substituents, it is possible to perform the methylenation without any additives (entry 11).[‌157‌]

‌Meeee 88‌ Meeeeeeeeeeee ee Meeeeeeee eee Meeeeee eeee Meeeeeeeeeeee–Meee Meeeeeee[‌888‌,‌888‌,‌888‌–‌888‌,‌888‌,‌888‌]

Meeee	Meeeeeee Meeeeeee	Meeeeeeeee	Meeeeee	Meeee (%)	Mee
8		MM8M8, Me, Me8Me, MMM, eeeeee, 88°M, 8 e		88	[‌888‌,‌888‌]
8		MM8M8, Me, Me8Me, MMM, eeeeee, 88°M, 8 e		88	[‌888‌]
8		MM8M8, Me, Me(MeMe)8, MMM, 88°M, 8 e		88	[‌888‌]
8		MM8M8, Me, MeMe8, MMM, 88°M, 88 eee		88	[‌888‌]
8		MM8M8, Me, MeMe8, MMM, 88°M, 88 eee		88	[‌888‌]
8		MM8M8, Me, MeMe8, MMM		88	[‌888‌]
8		MM8M8, Me, MeMe8, MMM		88	[‌888‌]
8		MM8(MeM)8, β-MeMe8, MMM		88	[‌888‌]
8		MM8(MeM)8, MeMe8, MMM		88	[‌888‌]
88		MM8(MeM)8, β-MeMe8, MMM, MMMMM, 88°M, 8 e		88	[‌888‌]
88		MM8(MeM)8 (8 eeeee), MMM, 88°M		88	[‌888‌]

Meeeeeeeeeee Meeeeeeee

8-Meeeeeeeeee-8-ee-8-ee Meeeeee (‌Meeee 88‌, Meeee 8); Meeeeee Meeeeeeee:[‌888‌,‌888‌,‌888‌]

MM8M8 (8.88 eM, 88 eeee) eee eeeee ee e eeeeeee eeeeeeeeee ee Me (8.8 e, 88 eeee) ee MMM (88 eM) ee 88°M eeeee ee eeeee eeeeeeeeee. Meeee 88 eee, e 8.8 M eeee ee MeMe8 (8.8 eeee) ee MM8Me8 eee eeeee ee 8°M, eee eee eeeeeeeee eeee eeeee eeeeeee eee eeeeeee ee 88°M eee 88 eee. M eeee ee eee eeeeeeeee eeeeee (8.88 e, 8.8 eeee) ee MMM (8 eM) eee eeeee eeeeeeee ee 88°M. Mee eeeeeeeee eeeeeee eee eeeeeee ee 88°M eee 88 eee eee eeee eeeeeee eeee Me8M (88 eM), eee eee eeeeeee eeeee eee eeeeee eeee 8 M MMe eeee (88 eM) eee eeeee. Mee eeeeeeeeeeee eeeee eeeeeee eee eeeeeeee ee eeeeeeeeeeeeee (eeeeee eee) ee eeee eee eeeeeee ee e eeeeeeeee eee; eeeee: 8.88 e (88%).

(8M,8M)-8-Meeeeeeee-8-eeeeee-8-eeeeeeeeeeeeeeeeeeee (‌Meeee 88‌, Meeee 8); Meeeeee Meeeeeeee:[‌888‌]

M eeeeeee ee Me (88 eeee), MM8M8 (8.8 eeee), eee MeMe8 (8.88 eeee) ee MMM (8.8 eM) eee eeeeeeeee ee ee eeeeeeeeee eeeeeeee eeee eeeee eeeee eee 8 e. Meee MM8M8 (88 eeee) ee MMM (88 eM) eee eeeee eeeeeeee ee 8°M eeee eeeeeeee eeeeeeee eeee 88 eee, eee eee eeeeeee eee eeeeeee ee 8°M eee 8 e. Meeee eee eeeeeeee eee eeeeeee, eee eeeeeeee eeeeee eee eeeeeee ee eeeee eeeeeeeeeee eee eeeeeee eeeee. Meeeee Me eee eeeeeeeee ee eeeeeeeeeeeee eee e 8M MMM eeeeeeee ee eee eeeeeeee eeeeeeeeeee eeeeee e eeeee eeeeeee ee δ −8.8 ee 8°M, eeeee eeeeeeeeeeee ee eee eeeeeeeee eeeeeee ee MM8(MeM)8. Mee eeeeeeeeeee eee eeeeeeeeee ee ee 8.8–8.8 M eeee eeeeeee ee MM8(MeM)8, eee eee MMM eeee eee eeee eee eeeeeee eeeeeeeee. Me eeeee ee eeee eeeeeeeee eee ee eeeee e eeeee ee e eeeeee eeeeeeee eeeeee.

MMM (8 eM) eee eeeee ee MeMe8 (8.88 e, 8.8 eeee) ee −88°M eeeee eeeee, eee eee eeeeeee eee eeeeeee ee 88°M eee 88 eee. Me eee eeeeeeee eeeeeeeeee eee eeeee MM8(MeM)8 (8.8 eeee) ee MMM ee 88°M, eee eee eeeeeeeee eeeeeee eee eeeeeee eee 8 eee. Mee eeeeee eeeeeeeee (8.8 eeee) ee MMM (8 eM) eee eeeee eeeeeeee ee 8°M, eee eee eeeeeee eee eeeeeee ee 88°M eee 8 e. Me8M (88 eM) eee eeeee, eee eee eeeeeee eee eeeeeeee eeeeeee e Meeeee eeeeee, eeeee eee eeeeee eeee Me8M (88 eM). Mee eeeeeeee eee eeeeeeeeeeee, eee eee eeeeeee eee eeeeeeee ee eeeee-eeeeee eeeeeeeeeeeeee (eeeeee eee); eeeee: 88%.

References