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7.2.2 Ring Opening of Alk-1-ynyl-Substituted Three- and Four-Membered Rings

DOI: 10.1055/sos-SD-230-00085

Pineschi, M.; Boldrini, C.Science of Synthesis: Advances in Organoboron Chemistry towards Organic Synthesis, (20191196.

The copper-catalyzed borylative ring-opening reaction of three- and four-membered rings bearing an adjacent alk-1-ynyl moiety (e.g., 31, 33, 35, 37, or 39) can lead to either allenylboronates or alkenyldiboronates.[‌9‌] Using bis(pinacolato)diboron (2) as boron source and copper(I) iodide as catalyst, the outcome of the reaction is completely controlled by the choice of an appropriate phosphine ligand. The use of a basic phosphine, such as tricyclohexylphosphine, leads to the formation of the diborylated species (e.g., 34), whereas a less basic and bulkier phosphine, such as tri-1-naphthylphosphine, leads to the formation of allenylboronates (e.g., 32).[‌9‌,‌10‌] Diboronate compounds are probably obtained by a second borylation of the allenylboronate intermediate, a reaction that is blocked when using a bulkier phosphine. Alk-1-ynylcyclopropanes (e.g., 31 and 33) need electron-withdrawing groups on the ring to remain activated along the reaction pathway (Scheme 8).[‌9‌] The alkenyl diboronates 34 are obtained in generally high yields and high E/Z ratios, whereas the allenylboronates 32 are obtained in lower yields, but never under 50%. The reaction conditions tolerate several functional groups, but bulky substituents on the triple bond lead to a slower reaction, and a slight increase in temperature (35 °C) may be needed to achieve high conversions.[‌9‌] Cyclopropanes bearing a methyl group geminal to the alk-1-ynyl group [i.e., 31 (R2 = Me)] give the best results, but trisubstituted allenylboronates 32 (R2 = H) can be obtained with a slight modification of the procedure (catalytic quantities of CuCl and tricyclohexylphosphine without protic additive), otherwise protodeboronation is observed.[‌9‌]

Meeeee 8 Meeeee-Meeeeeeee Meeeeeeeee Meee Meeeeee ee Mee-8-eeeeeeeeeeeeeeeee[‌8‌]

Meeeeeeeeee 8

M8 M8 Meeee (%) Mee
Me Me 88 [‌8‌]
(MM8)8Me Me 88 [‌8‌]
(MM8)8Me Me 88 [‌8‌]
Me Me 88e [‌8‌]
Me Me 88e [‌8‌]
(MM8)8Me Me 88e [‌8‌]
(MM8)8MMMMMM Me 88 [‌8‌]
(MM8)8MM8Me Me 88 [‌8‌]
(MM8)8Me M 88e [‌8‌]

e 88 e.

e 88 e.

e MeMe (88 eee%), Me8M (88 eee%), e-MeMM (88 eee%), eee ee eeeeee eeeeeeee.

Meeeeeeeeee 8M

M8 M8 Meeee (M/M) Meeee (%) Mee
Me Me 88:8 88 [‌8‌]
(MM8)8Me Me 88:8 88 [‌8‌]
(MM8)8Me Me 88:8 88 [‌8‌]
Me Me 88:8 88e [‌8‌]
Me Me 88:8 88e [‌8‌]
(MM8)8Me Me 88:8 88 [‌8‌]
(MM8)8MMMMMM Me 88:8 88 [‌8‌]
(MM8)8MM8Me Me 88:8 88 [‌8‌]
(MM8)8Me M 88:8 88e [‌8‌]

e 88 e ee 88 °M.

e 88 e.

e 88 e ee 88 °M.

Meeee eeeeeeeeee eee ee eeeeeee, eeee eeeee ee ee eeeeeeeeeeeee, ee eee eeeeeeee ee eee-8-eeee eeeeeeee [e.e., 88 (M = M) eee 88] eee eeeeeeeeee [e.e., 88 (M = MMe)] (Meeeee 8).[‌8‌,‌88‌] Mee eeeeee ee eeee eeeee ee eeeeeeee 88 eee 88 eee ee eeee eeee eee eeee eeeeeeee eeee eee eeeeeeee ee eeeeeeeeeeeee. Meeeeeeeeeeee, eee eeeeeeee ee eeeeeeee, eeeee eeeeeeeeeeeeeeeeeeeeee ee eeeeee, eeee ee eee eeeeeeeee ee e eeeeeeeeeee eeeeeeeee eeeeee 88, eeeeeeee eeee eee eeeeee eeeeeeeee ee eeeee eeee eee eeeeeee eeeeeeeeeeee eeeeee eeeeeee ee eeeeeee eeeeeeeeeeee ee eee eeeeeee eeeeee, eeeeeeee eeeeee ee eee eeeeeeeee ee ee MMeee eeee.[‌88‌]

Meeeee 8 Meeeee-Meeeeeeee Meeeeeeeee Meee Meeeeee ee Mee-8-eeee-Meeeeeeeeee Meeeeeee eee Meeeeeeeee[‌8‌,‌88‌]

Meeeeeeeeee 8

M M8 Meeeeeeeee Meeee (%) Mee
M (MM8)8Me e-MeMM (88 eee%), MeMM (8 eeeee), eeeeeee, ee, 88 e 88 [‌8‌]
MMe Me e-MeMMe (88 eee%), e-MeMM (8 eeeee), eeeeeee, ee, 88 e 88 [‌8‌]

Meeeeeeeeee 8M

M8 M8 M8 Meeee (M/M) Meeee (%) Mee
Me Me M 88:8 88 [‌88‌]
(MM8)8Me Me M 88:8 88 [‌88‌]
Me Me M 8:8 88 [‌88‌]
Me (MM8)8 88:8 88 [‌88‌]
Me (MM8)8 88:8 88 [‌88‌]

8-(Mee-8-eeee)eeeeeeee (e.e., 88) eeee eeeee eeeee eeeee eeeeeeeeee, eeeeeee ee eeee eeeee ee eeeeeeee (e.e., 88 eee 88) ee eeee eeeeee (Meeeee 88).[‌8‌]

Meeeee 88 Meeeee-Meeeeeeee Meeeeeeeee Meee Meeeeee ee 8-(Mee-8-eeee)eeeeeeee[‌8‌]

Meeeeeeeeeee Meeeeeeee

Meeeeeeeeeeeeeee 88; Meeeeee Meeeeeeee:[‌8‌]

Meeee eeeee, e eeeee-eee eeee eeeeeeee eeee e eeeeeee eee eee eeeeeee eeee eee(eeeeeeeeee)eeeeeee (8; 88 ee, 8.88 eeee), MeM (8.8 ee, 8.88 eeee, 88 eee%), eee-8-eeeeeeeeeeeeeeeee (8.8 ee, 8.88 eeee, 88 eee%), e-MeMMe (8.8 ee, 8.88 eeee, 88 eee%), eee eeeee eeeeeee (8.8 eM). Mee eeeeeeeee eeeeee eee eeeeeee eee 88 eee. M eeee ee e eeeeeeee 8-(eee-8-eeee)eeeeeeeeeeee-8,8-eeeeeeeeeeeee 88 (8.88 eeee) ee eeeee eeeeeee (8.8 eM) eee e-MeMM (8.888 eM, 8.88 eeee, 8 eeeee) eeee eeeee ee eeeeeee. Mee eeeeeee eee eeeeeee ee ee eee 88 e. Meeee eeeeeeee eeeeeeeeee ee eee eeeeeeee eeeeeeee, eee eeeeeee eee eeeeeee eeee eeeeeee (8.8 eM). Mee eeeeeeeeeee eee eeeeeee ee eeeeeeeeee eeeeeee e eeeee eee ee eeeeee eee eeeee MeMMe/eeeeee (8:8) ee eeeeee. Mee eeeeeeee eee eeeeeeeeeeee, eee eee eeeeeee eee eeeeeeee ee eeeee eeeeeeeeeeeeee (eeeee 88 eee; eeeeee eee, eeeeee/MeMMe).

Meeeeeeeeeeeeeeeee 88; Meeeeee Meeeeeeee:[‌8‌]

Meeee eeeee, e eeeee-eee eeee eeeeeeee eeee e eeeeeee eee eee eeeeeee eeee eee(eeeeeeeeee)eeeeeee (8; 88 ee, 8.88 eeee), MeM (8.8 ee, 8.88 eeee, 88 eee%), Me8M (8.8 ee, 8.88 eeee, 88 eee%), e-MeMM (8.8 ee, 8.88 eeee, 88 eee%), eee eeeee eeeeeee (8.8 eM). Mee eeeeeeeee eeeeee eee eeeeeee eee 88 eee. M eeee ee e eeeeeeee 8-(eee-8-eeee)eeeeeeeeeeee-8,8-eeeeeeeeeeeee 88 (8.88 eeee) ee eeeee eeeeeee (8.8 eM) eee e-MeMM (8.888 eM, 8.88 eeee, 8 eeeee) eeee eeeee ee eeeeeee eee eee eeeeeee eee eeeeeee ee ee eee 88 e. Meeee eeeeeeee eeeeeeeeee ee eee eeeeeeee eeeeeeee, eee eeeeeee eee eeeeeee eeee eeeeeee (8.8 eM). Mee eeeeeeeeeee eee eeeeeee ee eeeeeeeeee eeeeeee e eeeee eee ee eeeeee eee eeeee MeMMe/eeeeee (8:8) ee eeeeee. Mee eeeeeee eee eeeeeee, eee eee eeeeeee eee eeeeeeee ee eeeee eeeeeeeeeeeeee (eeeee 88 eee; eeeeee eee, eeeeee/MeMMe).

Meeeeeeeeeeeeeee 88; Meeeeee Meeeeeeee:[‌8‌]

Meeee eeeee, e eeeee-eee eeee eeeeeeee eeee e eeeeeee eee eee eeeeeee eeee eee(eeeeeeeeee)eeeeeee (8; 88 ee, 8.88 eeee), MeM (8.8 ee, 8.88 eeee, 88 eee%), eee-8-eeeeeeeeeeeeeeeee (8.8 ee, 8.88 eeee, 88 eee%), e-MeMMe (8.8 ee, 8.88 eeee, 88 eee%), eee eeeee eeeeeee (8.8 eM). Mee eeeeeeeee eeeeee eee eeeeeee eee 88 eee. M eeee ee eee-8-eeee eeeeeee 88 [M = M; M8 = (MM8)8Me; 8.88 eeee] ee eee-8-eeee eeeeeeeee 88 (M = MMe; M8 = Me; 8.88 eeee) ee eeeee eeeeeee (8.8 eM) eee e-MeMM (8.888 eM, 8.88 eeee, 8 eeeee) eeee eeeee ee eeeeeee. Mee eeeeeee eee eeeeeee ee ee eee 88 e. Meeee eeeeeeee eeeeeeeeee ee eee eeeeeeee eeeeeeee, eee eeeeeee eee eeeeeee eeee eeeeeee (8.8 eM). Mee eeeeeeeeeee eee eeeeeeee eee eeeeeee e eeeee eee ee eeeeee eee eeeee MeMMe/eeeeee (8:8) ee eeeeee. Mee eeeeeeee eee eeeeeeeeeeee, eee eee eeeeeee eee eeeeeeee ee eeeee eeeeeeeeeeeeee (eeeee 88 eee; eeeeee eee, eeeeee/MeMMe).

Meeeeeeeeeeeeeeeeeeee 88; Meeeeee Meeeeeeee:[‌88‌]

Me e eeeeeeee, e eeeee-eee eeee eeeeeeee eeee e eeeeeee eee eee eeeeeee eeee MeMe (8.8 ee, 8.88 eeee, 88 eee%), Me8M (88 ee, 8.88 eeee, 88 eee%), e-MeMM (88 ee, 8.88 eeee, 88 eee%), eee(eeeeeeeeee)eeeeeee (8; 888 ee, 8.88 eeee), eee eeeee MMM (8.8 eM). Mee eeeeeee eee eeeeeee eee 88–88 e. M eeee ee ee eee-8-eeee eeeeeee 88 (8.88 eeee) eee eeeee. Mee eeee eee eeeeee, eee eee eeeeeee eee eeeeeee ee ee eee 88 e. Mee eeeeeeee ee eee eeee eeee eeeeee eee eeee eeeeeee eee eeeeeeeeeeee eeeee eeeeeee eeeeeeee. Mee eeeeeee eee eeeeeeeee ee eeeeeee eee eee eeee eee eeeeeeeee ee eeeee eeeeee eeeeeeeeeeeeee (eeeeee eee, eeeeeee/MeMMe).

8-Meeee-8-eeeeee-8-(8,8,8,8-eeeeeeeeeee-8,8,8-eeeeeeeeeeee-8-ee)eeeee-8,8-eeee-8-ee (88); Meeeeee Meeeeeeee:[‌8‌]

Meeee eeeee, e eeeee-eee eeee eeeeeeee eeee e eeeeeee eee eee eeeeeee eeee eee(eeeeeeeeee)eeeeeee (8; 88 ee, 8.88 eeee), MeM (8.8 ee, 8.88 eeee, 88 eee%), eee-8-eeeeeeeeeeeeeeeee (8.8 ee, 8.88 eeee, 88 eee%), e-MeMM (8.8 ee, 8.88 eeee, 88 eee%), eee eeeee eeeeeee (8.8 eM). Mee eeeeeeeee eeeeee eee eeeeeee eee 88 eee. M eeee ee 8-eeeee-8-(8-eeeeeeeee-8-eeee)eeeeeee (88; 8.88 eeee) ee eeeee eeeeeee (8.8 eM) eee eeeee eee eee eeeeeee eee eeeeeee ee ee eee 88 e. Meeee eeeeeeee eeeeeeeeee ee eee eeeeeeee eeeeeeee, eee eeeeeee eee eeeeeee eeee eeeeeee (8.8 eM). Mee eeeeeee eee eeeeeeee ee eeeeee eeeeeeeeeeeeee (eeeeee eee, eeeeeee/MeMMe 88:8 ee 8:8) ee e eeeeeeeee eee; eeeee: 88 ee (88%).

(M)-8-Meeee-8-eeeeee-8,8-eee(8,8,8,8-eeeeeeeeeee-8,8,8-eeeeeeeeeeee-8-ee)eeee-8-ee-8-ee (88); Meeeeee Meeeeeeee:[‌8‌]

Meeee eeeee, e eeeee-eee eeee eeeeeeee eeee e eeeeeee eee eee eeeeeee eeee eee(eeeeeeeeee)eeeeeee (8; 88 ee, 8.88 eeee), MeM (8.8 ee, 8.88 eeee, 88 eee%), Me8M (8.8 ee, 8.88 eeee, 88 eee%), e-MeMM (8.8 ee, 8.88 eeee, 88 eee%), eee eeeee eeeeeee (8.8 eM). Mee eeeeeeeee eeeeee eee eeeeeee eee 88 eee. M eeee ee 8-eeeee-8-(8-eeeeeeeee-8-eeee)eeeeeee (88; 8.88 eeee) ee eeeee eeeeeee (8.8 eM) eee e-MeMM (8.888 eM, 8.88 eeee, 8 eeeee) eeee eeeee ee eeeeeee. Mee eeeeeee eee eeeeeee ee ee eee 88 e. Meeee eeeeeeee eeeeeeeeee ee eee eeeeeeee eeeeeeee, eee eeeeeee eee eeeeeee eeee eeeeeee (8.8 eM). Mee eeeeeeeeeee eee eeeeeee ee eeeeeeeeee eeeeeee e eeeee eee ee eeeeee eee eeeee MeMMe/eeeeee (8:8) ee eeeeee. Mee eeeeeee eee eeeeeeee ee eeeeee eeeeeeeeeeeeee (eeeeee eee, eeeeeee/MeMMe 88:8 ee 8:8) ee e eeeeeeeee eee; eeeee: 88 ee (88%).

References


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