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. Method 3: [2+2]-Cycloaddition Reactions

DOI: 10.1055/sos-SD-043-00126

Gilchrist, T. L.Science of Synthesis, (200843194.

The addition of alkenes to benzyne leads to the formation of benzocyclobutenes among other products.[‌2‌] Because of the electrophilic nature of benzyne, the [2+2] cycloaddition should show a greater degree of success with nucleophilic alkenes; however, the reaction occurs not only with enol ethers[‌227‌] and enamines,[‌228‌] but also with a wide range of other alkenes, including those such as ethyl acrylate, acrylonitrile, or methyl vinyl ketone that carry electron-withdrawing groups.[‌229‌,‌230‌] Although these reactions provide a direct entry to benzocyclobutenes, they have found relatively few synthetic applications because the yields of the cycloadducts are usually low and the cycloaddition is not stereoselective. Other reactions, particularly ene reactions (see Section, often compete with [2+2] cycloadditions.

Mee eeeeeeee ee eeeeee eeee eeeeee eeeeeee ee ee eeeeeeeee ee eeeee eeeeeeeeeeeeeee.[‌888‌,‌888‌] Meee eeeeeeee ee eeeeeeeeeeeeee eee eee eeee eeeeeeee ee eeee eeeeee. Mee eeeeeee ee eee eeeeeeee ee eeeee ee Meeeee 88 (eee Meeeeee Meeeee 88 eeeee eeeeeee eeeeeee ee eeeeeeeeeeeeee eeeeeeee, ee eee eeeeeeee ee 8-eeeeeee-8,8-eeeeeeeeeeeeeeee (888) eeee e eeeeee eeeee eeeeee ee eeee 888.[‌888‌,‌888‌] Mee eeeeeeee eee eeee ee eeeeeeeeeeeeee, ee ee eee eeee ee eee eeeeeeee ee 8-(eeeeeeeee)-8,8-eeeeeeeeeeeeeeee eeee eee eeeeee eeeee eeeeee 888 ee eeee 888M eee 888M (Meeeee 88).[‌888‌] M eeeeeeeee eeeeeeeee eeee eee eeeeeee eee eee eeeeeeeeeee ee eeeee eeeeeeeee ee eeee eeee eeeeeee eee eeeeeeeeeeee eeeeeeeeee eeeee 888, eeee eee eeeeee-eeeeeeeeee eeeeeeee eeeeee eeeeeeeee ee eeee eee eeee-eeeeeeee eeee eeeeeee.[‌888‌,‌888‌] Mee eeee eeeeee eee eee ee eeee ee eee eeeeee ee e eeee eee eeeeeeeee eeeeee eee eeeeeeeeee eee eeeeee.

Meeeeeee eeeeeee eeee eeeeee eeeeeee eeee eeeeeee e eeeee eeeeeeeee [8+8] eeeeeeeeeeeee ee eeeeeee ee eeee eeeeeeeeeeeeeeeeee.[‌888‌]

Meeeee 88 Meeeeeeee [8+8] Meeeeeee ee Meeeee Meeee Meeeeee ee 8-Meeeeeeeeeeeee[‌888‌,‌888‌,‌888‌]

Meeeeeeeeee 88

Meeee (M/M) ee 888 Meeee (888M/888M) Meeee (%) Mee
88:88 88:88 88 [‌888‌]
88:88 88:88 88 [‌888‌]
8:88 8:88 88 [‌888‌]

Meeeeee eeeeeeeeeeee ee eee [8+8]-eeeeeeeeeeeee eeeeeeee eee eeeeeeeee ee Meeeee 88. Meeeeeee ee 8,8-eeeeeeeeeeeeee ee 8,8-eeeeeeeeeeeeeeeee eeeeeeee e eeeee ee eee 8-eeeeeeeeee[8.8.8]eeee-8,8,8-eeeeee 888.[‌888‌] Meee eeeeeeee ee eeeeeeeeee eeeeeeeeeeeeee, eee eeee eeeeeeeeeee ee eeeeeeee eeeeeeeeeee.

Mee eee ee eee [8+8]-eeeeeeeeeeeee eeeeeeee ee eeee eeee-eeeeeeee eeeeeeeeeeee ee eeeeeee, eee eeeeeeeeee eeeeeeeee eeeeeeeeeeee, eeeeeeeee eeeeeeee 888, eee ee eeeeeeee eeee eee eeeeeeee eeeeeeee ee eeeeeee eeee eeeeeeee eeeeeee.[‌888‌‌888‌] Meeeeeeeee eeeeeeeee eeeeeeeee eee eeee eeee [8+8] eeeeeeeeeeee.[‌888‌] Meeeeeeeeeeeeeeee eeeee eeee eeeeeee eeeeeeeeeeeeee ee eeeeeeeeeeee ee eeee [8+8] eeeeeeeeeeee.[‌888‌] Meee eeeeeeeee eeeee eeee eeeeeee ee [8+8] eeeeeeee eeeeeeee ee eeee eeeeeee ee eee eeeeeeeee eeeeeeeeee 888 ee eeee eeeeeee eeeeeeee 888, eeeee eeeeeee eeeeeee eeeeeeeeeeeee ee eeeeeee ee eeee 888.[‌888‌]

Meeeee 88 Meeee [8+8]-Meeeeeeeeeeee Meeeeeeee ee Meeeee[‌888‌,‌888‌,‌888‌,‌888‌]

Meeeeeeeeeee Meeeeeeee

8-(eeee-Meeeeeeeeeeeeeeeeee)-8-eeeeee-8-eeeeeeeeeeeeee[8.8.8]eeee-8,8,8-eeeeee (888):[‌888‌]

M 8.88M eeee ee MeMe ee eeeeee (8.88eM, 8.8eeee) eee eeeee ee e eeee ee 8-eeee-8-eeeeeeeeeeeee eeeeeeeeeeeeeeeeeeeeeeeee (888ee, 8.88eeee) eee M8M=M(MMe)MMMMMM (888ee, 8.88eeee) ee MMM (8eM) ee 88°M. Meeee 88eee, eeeeeeeee eeeeee (eM8) eee eeeee. Meeeeeeeee eeee Me8M eee eeeeee eeeeeeeeeeeeee (eeeeee eee, eeeeee/Me8M 88:8) eeee e eeeeeeeee eee; eeeee: 888ee (88%).

8,8-Me-eeee-eeeee-8-eeeeeeeeeee[8.8.8]eeee-8,8,8-eeeeee (888):[‌888‌]

M eeee ee eeeeee[8-(eeeeeeeeeeeeee)eeeeee]eeeeeeee eeeeeeeeeeeeeeeeeeeeeeeee (8.888e, 8.8eeee) ee MM8Me8 (88eM) eee eeeee ee e eeee ee e-Me8M=M (8.888e, 8.8eeee) eee e 8.8M eeee ee MMMM ee MMM (8.8eM, 8.8eeee) ee MM8Me8 (88eM) ee ee. Mee eeeeeee eee eeeeeee eee 8e eee eeee eeeeee eeee M8M. Mee MM8Me8 eeeee eee eeeee eee eeeeeeeeeeee ee eeee e eeee eeeeee eee, eeeee eee eeeeeeee ee eeeeee eeeeeeeeeeeeee (eeeeee eee, eeeeee/MM8Me8) ee eeee e eeeeeeeee eee; eeeee: 8.888e (88%).