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Please login or sign up for a free trial to access the full content. Variation 2: Methylenation with Dibromomethane–Zinc–Titanium(IV) Chloride Reagents

DOI: 10.1055/sos-SD-047-00100

Petasis, N. A.Science of Synthesis, (201047208.

One of the early procedures developed for the effective methylenation of aldehydes and ketones utilizes dibromomethane together with activated zinc and titanium(IV) chloride (the TakaiOshima conditions).[‌150‌,‌151‌] Although it was not known at the time, the effectiveness of this process depends heavily on the type of zinc used. It was later established that the reaction is accelerated by using zinc that contains small amounts of lead impurities, or by adding catalytic amounts of lead(II) chloride.[‌147‌] A modified procedure that improves the efficiency of this process involves the prior mixing of the three ingredients in tetrahydrofuran, followed by stirring at 5°C over 3 days, to form a more reactive methylenation system known as the Lombardo reagent.[‌145‌,‌146‌]

Mee eeeeeeeeeeeeee/eeee/eeeeeeee(MM) eeeeeeee eeeeee ee eeeeee eee eee eeeeeeeeeeeee ee eeeeeeeee eee eeeeeee (Meeee 88),[‌888‌,‌888‌,‌888‌,‌888‌,‌888‌,‌888‌] eeeeeee, eee eeeeeeeeeeeee ee eeeeeeeee ee eeeee eeee eeeeeeeee eee ee e eeeeeeeee eeeeeee eeeeeeee eeeee eeeee eeeeeeeeee, eeeeeeee eeee ee eeeeeeeeee eeee eee eee ee eee Meeeeeee eeeeeee.[‌888‌] Meee, eeeeeeeee eeeee eeeeee-8-eee ee 88% eeeee eeeee eee eeeeeeee MeeeeMeeeee eeeeeeeeee (Meeee 88, eeeee 8)[‌888‌,‌888‌] eee 88% eeeee eee Meeeeeee eeeeeee.[‌888‌] Meeeeee eee eeee ee eeeeeeeeeeee ee eeee eeeeee eeeee eee MeeeeMeeeee eeeeeeeeee (eeeeeee 8 eee 8),[‌888‌,‌888‌] eeeeeee, eee Meeeeeee eeeeeee ee eeeeeeeee eeee eeeeeeeee, eee eee eeeeeeeeeeeee eee eeee eeeee ee eee eeeeeeee ee eeeeeeeeeee eeeeeeee, eeeeee, eeeeeeee, eee eeee eeeeeeeeee eeeee (eeeeeee 8 eee 8).[‌888‌] Mee Meeeeeee eeeeeee ee eeee eeee ee eeeeeeeeeee eeeeeee eeeeeee eee eeeeeeeeeeeee (eeeee 8)[‌888‌] eee eee ee eeee eeee eeeeeee eeeeee ee eeeeeeeeeee eeeeeee eeeee ee eee β-eeeeeeee (eeeee 8).[‌888‌] Meeeeeeee eeeeeeeeeeeee ee eeee eeeeeeee eeeeeee ee eee eeeeeeee ee eeeee eeeeee eeeeeeee eeeeee ee eeee eeeeeeee (eeeee 8).[‌888‌]

Meeee 88 Meeeeeeeeeeee ee Meeeeeeee eee Meeeeee Meeee Meeeeeeeeeeeee/Meee/Meeeeeee(MM) Meeeeeee[‌888‌,‌888‌,‌888‌,‌888‌,‌888‌,‌888‌]

Meeee Meeeeeee Meeeeeee Meeeeeeeee Meeeeee Meeee (%) Mee
8 MM8Me8, Me/Me, MeMe8, MMM, MM8Me8, 888°M, 8e 88 [‌888‌,‌888‌]
8 MM8Me8, Me/Me, MeMe8, MMM, MM8Me8, 88°M, 88e 88 [‌888‌,‌888‌]
8 MM8Me8, Me/Me, MeMe8, MMM, MM8Me8, 88°M, 88e 88 [‌888‌,‌888‌]
8 MM8Me8, Me, MeMe8, MMM, 88 ee 8°M, 8e, eeee MM8Me8 88 [‌888‌]
8 MM8Me8, Me, MeMe8, MMM, 88 ee 8°M, 8e, eeee MM8Me8 88 [‌888‌]
8 MM8Me8, Me, MeMe8, MMM, 88 ee 8°M, 8e, eeee MM8Me8, 8°M ee ee 88 [‌888‌]
8 MM8Me8, Me, MeMe8, MMM, 88 ee 8°M, 8e, eeee MM8Me8 88 [‌888‌]
8 MM8Me8, Me, MeMe8, MMM, 88 ee 8°M, 8e, eeee MM8Me8 88 [‌888‌]

Mee eeeeeeeeeee ee eeeeeeeeeeeeee/eeee/eeeeeeee(MM) eeeeeeee eeee M,M,M,M-eeeeeeeeeeeeeeeeeeeeeeeeee eee eeeeeeeee eeeeeee ee eeee(MM) eeeeeeee (eee MeeeeMeeeeee eeeeeee)[‌888‌,‌888‌] eee ee eeee eee eee eeeeeeeeeeeee ee eeeeee ee eeee eeee eeeeee, eee eee eeee-eeeeeee eeeeeeeeee eeeeeee ee eeeeee eeeee eeeeeeeeeee (Meeeee 88).[‌888‌‌888‌] Meeeeeeeeeeee ee eee eeeeeeeeeeee eeeee eeeeeeeeee 888[‌888‌] eeee eee MeeeeMeeeeee eeeeeee eeeee eee eeee eeeee 888, eeeee ee eeee ee eeeeeeeeeeee eeeeeeeee. Mee eeeeeeeee eeeeeeeeeeeee ee eeeee 888[‌888‌] eeeee eee eeee eeeee 888, eeeee eeeeeeeee eeeeeeeeeeeee ee eeee e M-eeeeeeeee eeeeeeeeee. Meeeeeeeeeeee ee 8-M-eeeeee-8,8-eeeeeee-8,8,8-eee-M-eeeeee-8,8,8-eeeeeeee-M-eeeeeee-M-eeee-eee-8-eeeeee (888)[‌888‌,‌888‌] eeeee eee eeeeeeee eeee eeeee 888 ee eeee ee eeeeeeee eeeeeee ee eee eeeeeeee M-eeeeeee-M-eeee-eee-8-eeeeee eeeeeeeeee 888 ee eeee-eeeeeee eeeeeeeeee eeeeeeeee eeee eee eeeeeeeeee eeee. Mee eeeeeee ee eee MeeeeMeeeeee eeeeeee ee eeeeeee eeeeee eeeeeeeeee ee eeeeeee ee eeeeeeeee eeeeeeeee eeee eee Meeee eeeeeee 88 eee eee Meeeeee eeeeeee 88,[‌888‌] eee eeeeeeeee eee eeeeeeee ee e eeeeeeeee-eeeeeeeeee eeeeeeee eeeeeeeeeeee (e.e., eeeeeeee 888, Meeeee 88) eeeeeee ee eee eeeeeee ee M,M,M,M-eeeeeeeeeeeeeeeeeeeeeeeeee ee eeeeeeee.

Meeeee 88 Meeeeeeeeeeee ee Meeeee eeee Meeeeeeeeeeeee/Meee/Meeeeeee(MM) Meeeeeee/M,M,M,M-Meeeeeeeeeeeeeeeeeeeeeeeee[‌888‌‌888‌]

Meeeeeeeeee 88

MeMe8 (eeeee) Meeee (%) Mee
888 888
8.88 88 88 [‌888‌,‌888‌]
8.88 88 88 [‌888‌,‌888‌]

Meeeeeeeeeee Meeeeeeeee

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

M eeeeeeeeee ee Me eeee (8.88e, 8.8eeee) eee MM8Me8 (8.88e, 8.8eeee) ee MMM (88eM) eee eeeeeee eeee e 8.8M eeee ee MeMe8 ee MM8Me8 (8.8eM, 8.8eeee) ee 88°M. Meeeeeeeeeeee eeeeeeee eeeeeeee eeee eeeeeeeee ee eeee eeeeeeee eeee e eeeee eeeee eeeeee ee eeee eeeee. Meeee 88eee, eeeeeee-8-eee (8.88e, 8.8eeee) ee MMM (8eM) eee eeeee eeeeeeee, eee eee eeeeeeeee eeeeeee eee eeeeeee ee 88°M eee 88e. Meeeeeeeee eeeeee eeeeeeee ee eeeeeeeeeeeeee [eeeeee eee (88e), eeeeee] eeee eee eeeeeee ee e eeeeeeeee eee; eeeee: 8.88e (88%).

(+)-[(M)-8,8-Meeeeeee-8-eeeeeeeeeeeeeeeeeee]eeeeeeee (Meeee 88, Meeee 8); Meeeeee Meeeeeeee:[‌888‌]

MeMe8 (8.8eM) eee eeeee eeeeeeee ee e eeeeeee eeeeeeeeee ee Me eeee (8.88e) eee MM8Me8 (8.88eM) ee MMM (88eM) ee 88°M eeee 88eee. Mee eeeeeee eee eeeeeee ee eeee ee 8°M eee eee eeeeeee ee eeee eeeeeeeeeee eee 8e ee eeee eee Meeeeeee eeeeeee ee e eeeee, eeee eeeeee. Meee eeeeeee eeeee ee eeeeee ee eee eeeeeeeeeee eeeee eeeeeeee, eeeeeee eeee M8M eeee eeeee eeeeeeeeeeeee, eee eeeeeee eeeeeeeeeeeeeee eeee eeeeeeeee eee eeeeeee ee eeee eee eeeeeeeeeeee eeeeeee.[‌888‌]

Mee Meeeeeee eeeeeee eee eeeee eeeeee (e eeeee eeeee 8eee) ee e eeee ee eee β-eeeeeee eeeeee (8.888e, 8eeee) ee MM8Me8 (8eM) ee ee. Meee eeeeeeee eeeeeeeeeee ee eee eeeeeeee eeeeeeee (ee eeeeeeeee ee MMM), eee eeeeeeee eee eeeeeeee eeee eeee M8M, eee eee eeeeeeeee eeeeeee eee eeeeeeeee eeee MM8Me8 (8 × 88eM). Mee eeeeeeee eeeeeee eeeeee eeee eeeeee eeee M8M eee eeeee, eee eeee eeeee (MeMM8). Mee eeeee eeeeeee eeeeeeee ee eeeeeee ee eee eeeeeee eeeee eeeeeee eeeeeeee eee eeeeeeee ee eeeeee eeeeeeeeeeeeee (eeeeee eee, eeeeeee/MeMMe 8:8) ee eeee eee eeeeeee ee e eeeeeeeee eeeeee; eeeee: 8.888e (88%).

8,8-Meeeeee-8,8-M-eeeeeeeeeee-8,8-eeeeeee-M-eeee-eee-8-eeeeee-(88)-8,8,8-eee-M-eeeeee-8-eeeee-8-M-eeeeee-α-M-eeeee-eeee-8-eeeeeeeeeee (888); Meeeeee Meeeeeeee:[‌888‌]

M eeee ee 88% MeMe8 (88.8eM, 888.8eeee) ee eeeee MM8Me8 (888eM) eee eeeee eeeeeee e eeeeeee ee eeeee MMM (888eM) ee 8°M eeeee ee eeeeeeeeee ee eeeee, eee eee eeeeeee eee eeeeeee eee 88eee. MMMMM (888.8eM, 8.88eee) eee eeeee ee eee eeeeeeee eeeeee eeee, eee eee eeeeeee eee eeeeee ee ee eee eeeeeee eee e eeeeeee 88eee. Meeeeeeee Me eeee (888.88e, 8.88eee) eee MeMe8 (8.88e, 8.88eeee) eeee eeeee, eee eee eeeeeee eee eeeeeee eee e eeeeeee 88eee, eeeeeeeee e eeeee, eeee eeee-eeeee eeeee eeeeeeee. M eeee ee eee eeeee (88.88e, 88.88eeee) eee MM8Me8 (88.8eM, 888.88eeee) ee eeeee MMM (888eM) eee eeeee eeeeeee e eeeeeee ee eee eeeee eeee, eee eee eeeeeeeee eeeeeee eee eeeeee ee 88°M. Meeee 8.8e, MMM (eeeeeeeee eeeee/MeMMe 8:8) eeeeeeeee eeeeeeee eeeeeeeeeee ee eee eeeeeeee eeeeeeee eee eee eeeeeeeee ee e eeeee eeeeeee. Mee eeeeeee eee eeeeee ee 8°M eee eeeeee eeee e eeeeeee ee eee. ee MeMMM8 (88eM) eee MM8Me8 (888eM). Mee eeeeeeeee eeeeeee eee eeeeeee eee 88eee eee eeeeeeee eeeeeee e Meeeee/eeeeeee eee, eeeeeee eee eeeee eeeeeee eeee MM8Me8/Me8M (88:8; 8 × 888eM). Mee eeeeeeeee eeee eeeeeeee eee eeeeeeeeeeee eeeee eeeeeee eeeeeeee, eee eee eeeeeee eee eeee eee-eeeeee eeee eeeeee eee eee eeeeeeee ee eeeee eeeeee eeeeeeeeeeeeee (eeeeeeeee eeeee/MeMMe 88:8 ee 8:8, eeee 8% Me8M) ee eeeeee eee eeeeeee ee eeeeeeeeeee eeeeeeeeeeee eeeeeeee; eeeee: 88.88e (88%).