0 Hits

  • Previous / Next

You are using Science Of Synthesis as a Guest. Please login or sign up for a free trial to access the full content. Three-Component Hetero-[4 + 2]-Cycloaddition/Allylboration Approach

DOI: 10.1055/sos-SD-211-00113

Szabó, K. J.Science of Synthesis: Multicomponent Reactions, (20142367.

Another efficient procedure for in situ generation of allylboronates has been presented by Hall and co-workers.[‌21‌,‌22‌,‌74‌‌76‌] In this reaction, a [4 + 2] inverse-electron-demand cycloaddition of a heterodienylboronate and electron-poor alkenes is performed to produce cyclic allylboronates 23 (Scheme 13). The allylboronates can be reacted with aldehydes without isolation to give the corresponding homoallylic alcohols 24. A particularly attractive feature of this reaction is that using catalyst 22, which was introduced by Jacobsen and co-workers,[‌77‌] enantiomerically pure allylboronates can be obtained.[‌22‌,‌74‌‌76‌] Thus, the procedure is suitable for the synthesis of chiral dihydro-2H-pyrans 24 (X = O) and tetrahydropyridines 24 (X = NR2) from allylboronates. The reaction has a very broad scope as a large variety of alkenes, including chiral ones,[‌75‌] can be employed (in the latter case, the reaction proceeds without the chromium catalyst).

Meeeee 88 Meeeeee Meeeee eee Meeeʼe Meeeeeeeeeeee/Meeeeeeeeeeeeee Meeeeee[‌88‌,‌88‌,‌88‌‌88‌]

Mee eeeeeeee ee eeeeeeeee eeee ee 88 eeee eeeeeeeee eeeeeeee eeee eeeeeeeee eeeeeeeeeeeeeeeee. Meee eee eeeeeeee ee eeeeeeeee eeee eeeeee eeeeeeeeeeeeee, e eeee eeeeeeeee eeeeeeee ee eee eeeeeeee (e.e., 8,8-eeeeeee-8M-eeeeee 88) eeeeee (Meeeee 88). Meee eee ee-eeeeeee eeeeeeeeeeee eeee eeee eeeeeeee eeeeee ee eeeeeeeee eeeeeeeeeee eee eee eeeeeeeee ee eeeeeee eeeeeee eeeeeeee, eeee ee eeeeeeeeee-eeeee eeeeeeeeee eeeeeeeee[‌88‌] eee eee eeeee-eeeee eeeeeeeeeee eee eeeeeeeee eeeeeeeeeee, eeee ee eeeeeeeeee eee eeeeeeeeee eeeeeeeee, eeeeeeeeeeee.[‌88‌]

Meeeee 88 Meeeeeeee ee Meeeee 8,8-Meeeeee-8M-eeeee Meeeeeeeeee[‌88‌]

Meeeeeeeeee 88

M8 Meee (°M) Meeee (%) Mee
Me 88 88 [‌88‌]
8-M8MM8M8 88 88 [‌88‌]
8-MeMM8M8 88 88 [‌88‌]
(MM8)8Me 88 88 [‌88‌]
MMMM8 88 88 [‌88‌]

Mee eeeeeeee eee ee eeeeeee eee eeee e eeeee eeeeeee ee eeeeeeeee eeeeeeeee eeeeeeee, eeeeeeeee, eee eeeeeee eeeeeee (Meeeee 88). Me eee eeee ee eeeeeeeee eeeeeeeee, eeee ee 8-eeeeeeeeeeeeeeeee ee eeeeeeee, eee eeeeeeee eee ee eeeeeee eee ee eeee eeeeeeeeeee, eeeeeee eeeeeeeeeeee eeeeeeeee eeeee ee eeeeeeee eeeeeeee eeeeeeeeeee.

Meeeeeeeeeee Meeeeeeee

(M)-[(8M,8M)-8-Meeeee-8,8-eeeeeee-8M-eeeee-8-ee](eeeeee)eeeeeeee (88, M8 = Me); Meeeeee Meeeeeeee:[‌88‌]

Meeeeeee 88 (8.88 ee, 8.888 eeee) eee eeeeeeee MeM (888 ee) eeee eeeee ee e eeeeeee ee (M)-8-(8,8,8,8-eeeeeeeeeee-8,8,8-eeeeeeeeeeee-8-ee)eeeeeeee (888 ee, 8.88 eeee) eee eeeee eeeee eeeee (8.88 eM, 88.8 eeee) ee ee eeee-eeeee, 88-eM, eeeee-eeeeeeee eeeee eeeeeeeeee e eeeeeee eee. Meeee eeeeeeee ee 88 °M eee 8.8 e, eeeeeeeeeeee (888 ee, 8.88 eeee) eee eeeee ee eee eeeeeee. Mee eeeeeee eee eeeeeee ee 88 °M eee 88 e, eeee eeeeeee eeee MeMMe, eee eeeeeeee eeeeeee Meeeee. Mee MeMMe eeee eee eeeeeee eee 88 eee eeee eee. ee MeMMM8. Meeee eeee eeee, eee eeeeeee eeeee eee eeeeeeeee eee eee eeeeeee eeeee eee eeeeeeeee eeee MeMMe (8 × 88 eM). Mee eeeeeeee eeeeeee eeeeee eeee eeeeee eeee eee. ee MeMe (88 eM), eeeee (MeMM8), eeeeeeee, eee eeeeeeeeeeee ee eeeeee eee eeeee eeeeeee. Meeeeeeeeeee ee eeeee eeeeee eeeeeeeeeeeeee (eeeeeeeeeee eeeeee eee, eeeeeee/Me8M 8:8) eeee eee eeee eeeeeee ee e eeeee eee; eeeee: 888 ee (88%).