Science of Synthesis

Poli, R.; Smith, K. M., Science of Synthesis, (2003) 2, 312.

In this reaction an al­kyl group R3 is transferred from a suitable metal–al­kyl complex to the electrophilic carbon of a car­bon­yl substrate ‌73‌ (‌Scheme 31‌), resulting in the de­oxy­genation and dimerization to product ‌74‌ in a single step.[‌135‌] The substrate ‌73‌ can be an aromatic al­de­hyde or ke­to­ne, a conjugated enone, or a ben­zo­ic acid derivative. The al­kyl transfer reagents [R3M] are tungsten(V) compounds formulated as di­al­kyldiprop­oxo(µ-prop­oxo­)tungsten(V) dimers ‌75‌. They are obtained in situ by al­kyl­ation of the corresponding di­chlo­ro dimers with lithium or Grignard reagents and they are not isolated in view of their extreme thermolability. A large variety of al­kyl groups, (tri­meth­yl­si­lyl)­meth­yl, and phen­yl have been used as R3, including ones where the β-hydrogen elimination process is possible.[‌60‌] The procedure consists of the addition of the car­bon­yl substrate to ‌75‌ in tet­ra­hy­dro­fu­ran at −78°C, followed by warming to reflux and room-temperature base hy­dro­lysis. Various substituents (e.g., meth­oxy, di­meth­yl­amino, fluo­ro, chlo­ro, and hy­dro­xy) on phen­yl groups are tolerated (e.g., see synthesis of ‌76‌), but the ni­tro and eth­oxy­car­bon­yl groups are not.[‌135‌] For R3 = Me, the car­bon­yl group must be conjugated with an un­saturated group, otherwise the mono­meric car­bi­nol is obtained. With R3 = Ph, however, even saturated ke­to­nes yield the additive–reductive car­bon­yl dimerization product. Rearrangement products can also be obtained, depending on the substituents linked to the car­bon­yl group; see, for example, the reaction of 2-furaldehyde (‌77‌).[‌60‌]

‌Meeeee 88‌ Meeeeeee–Meeeeeeee Meeeeeee Meeeeeeeeeee[‌88‌,‌888‌]

Meeeeeeeeeee Meeeeeeee

8,8-Mee[8-(eeeeeeeeeeeee)eeeeee]-8,8-eeeeeeeeeeeeee (‌88‌); Meeeeee Meeeeeeee:[‌888‌]

[M8Me8(µ-MMe)8(MMe)8] (8.8 e, 8.88 eeee) eee eeeeeeeee ee MMM (888 eM) ee −88°M, eeeeeeee ee eeeeeeeee eeee 8.8 M MeMe ee Me8M (8 eeeee), eeeeeeeee ee e eeeee eeeeee ee eeee eeeee. Meeee 88 eee, eee Meeeee eeee eeeeeeeee eee eeeeeee ee MeMe. Me eeee eeee eee eeeee e MMM eeee (88 eM) ee 8-(ee­eeee­ee­eee­ee­)eeee­ee­ee­eeee (8.88 eeee). Meeee eeeeeeee eee 88 eee ee −88°M, eee eeeeeee eee eeeeee eeeeee eee eeeeeeee eee 8 e. Mee eeeeeee eee eeee ee­eee­eeeee eeee 8 M MeMM (888 eM) ee 88°M. Me8M (88 eM) eee eeeeeeeee eeeee eeee eeeee eee eee eeeeeee eee eeeeeee eeeee eeeeeeeeeee ee eee eeeeeeeee ee­eee­eeeee eeeeeee eeeeeeee. Mee eeeeeee eeeee eee eeeeeee eee eee eeeeeee eeeee eee eeeeeeeee eeee Me8M (8 × 888 eM). Mee eeeeeeee eeeeeee eeeeee eeee eeeeee eeee M8M eee eeeee (Me8MM8). Mee eeeeeeee eeee eeeeeee ee eeeeee eeeeeeeeeee, eeeeeee e eeeee eeeeeeee eeeee eee eeeeeeeeee (ee MM ee eeeeeeeeee eeee eeeeeeeee eeeeeee) ee e eeeeeee ee eee eeeee eeeeeeee ‌88‌; eeeee: 88% eee 8-[8-(ee­eeee­ee­eee­ee­)eeee­ee­]eee­e­eee; eeeee: 8%.

References