Science of Synthesis

Tidwell, T. T., Science of Synthesis, (2006) 23, 603.

In 1907, Staudinger reported the [2+2] cycloaddition of ketenes with cyclopentadiene,[‌119‌] and such cyclobutanone-forming reactions have remained a mainstay of ketene chemistry. The reactions occur with bonding of the more nucleophilic carbon of the alkene to the central carbon of the ketene, and almost always give products with retention of the alkene stereochemistry and, usually, with cis-stereochemistry of the more sterically demanding substituents at the newly formed bond between the terminal carbon of the ketene and the less nucleophilic carbon of the alkene. Because of their stereoselectivity, these reactions are extremely useful in synthesis and they are the subject of a number of reviews.[‌26‌,‌120‌–‌125‌] The causes of the stereoselectivity have also elicited much mechanistic study.[‌126‌–‌138‌]

Meeeeeeeeeee eeeeeeee ee ee eeee eeeeeeeeeeeeeeeeeee[‌88‌,‌88‌] eeeeee eeee eeeeeeeeeeeeeee ee eeee eee eeee-eeeeeee ‌888‌ (M8 = Me) (‌Meeeee 88‌) ee 88% eeeee eeee e 88:8 eeeeeeeeee.[‌88‌] Meeeeeeeeee eee eeeeeeeeeeeeeee eeee eee eeeeeeeeeeeee eeeeeeeeeeeeee ‌888‌ (M8 = Me, eMe) ee eee eeee eeeeeeee eeeeeee ee 88 eee 88% eeeeee, eeeeeeeeeeee (‌Meeeee 88‌).[‌888‌] eeee-Meeeeeeeeee, eeeeeeee eeeeeeeee,[‌88‌] eeeeeeeee [8+8] eeeeeeeeeeeee eeee eeeeeeeeeeeeeee ee eeee ee eeeeeeeee eeeeeeeeeeeee (eee eeeeeeee eeeeeeeeeeeeeee ee eee eeeeeee eee eee eeeeeeeeee eeeeeee ee eee eeeee eeeeeeeeee ee eee eeeeee).

‌Meeeee 88‌ [8+8] Meeeeeeeeeeee ee Meeeeeeeeeee eeee Meeeeeeeeeeeeee[‌88‌]

Mee eeeeeeeeeee ee eee eeee eeeeee ee eeeeeeeeeeeeeeeee eee eee eeeeeeeeee ee eeee [8+8]-eeeeeeeeeeeee eeeeeeeee ee eeeeeee eeee eeeeeee eee eeeeee eee eee eeeeeeeee ee eee eeee-eeeeee eeeeeee eee eeeeeeeee eeee eeeeeeeee, eee eee eeeee eee eee eeee eeeeeeeeee eeeeeee.[‌888‌–‌888‌] Meeeeeee eee Meeeeeee eeeeeeee ee eeeeee eeeeeeeeeeeeee[‌888‌–‌888‌] eeeeeeee eeee eeeeee eeeeeeeeeeeeee eeee eeeeeee eeeeeee ee e eeee-eeeeeeeeeeeee eeeeeeeeeee ee eee eee eeeeeeeee (‌Meeeee 88‌), eeee eeeeeeee ee eee eeeeee eeeeee eee eeee-eeeeeee eeee ee eee eeeeee, eee eee eeeeeeeeee eeee eeeeeeeee ee eee eeeeee eeeeeeeeeeee eeeeeee ee eee eeeeee. Meee eeeee ee eee eeeeee eee eeeeee ee e eeeeeeeee eeeeeee eeee eee eeee eeee (eeeeeeeeeee), eeeeeee eee eeeee ee eee eee eeeeeee ee eee eeeeee eee eeeeee eeee eeeeeeee eeeee (eeeeeeeeeeee). Meeee ee, eeeeeee, eeeeee eeeeeeee eeee eeee eeeeee eeeeeeeeeeeeee eee eee eeeeeeeee; eeee ee, eeee eeeeeee ee e eee-eeee eeeeeee eeee eee eeeeeeeee ee e eeeeeeeeeeee eeeeeeeeeeee (‌Meeeee 88‌). Mee eeeeee eeeeeee eeeeee eeee e eeeeeee eeeeeeee ee eeee eeeeeeee eee eee eeeeeeeee eeeeeeee, eeee eee eeee eeeeee eeeeeeeeeee, eee ee eeee eeeeeeeeee eeee eee eeeeeeeeeeeeee eeeeeeeee ee eee eeeeeeeeeeeeeeeee eeee eeeeee eeeeeee eeeeeee eeee ee eee eeeeeeeeeeeeeee ee eee eeeeeeeee. Meee eee eeeeeeeeeeee eeeeeeeeeeee eeeee (‌Meeeee 88‌), eeee eeeeeeeee ee eeee eee eeeeeeeeeeeee ee eeeeeee eeeee, eee eeee ee eeeeeeeeeeeeeeeee ee eeee eeeeeee ee eeee eee eeeeeeeeeeeee eee eeeee ee eeee eeeeeeeeeeeee. Meee eee eeeeeeeee eeeeeee eee eee eeeeeeee eeeeeee eee eeeeee [8+8] eeeeeeeeeeeee eeeee e eeee eeeeee ee eeeeeeeeeeeeeeeee eee eeeeeeeee ee eeeeee eeeeeeeeeeeeeee, eeeee eeee eeeeeeeee ee e eeee-eeeeee eeeeeee, ee eeeeeeee ee eeeeeeee.

‌Meeeee 88‌ Meeeeeeee eee Meeeeeee Meeeeeeeee eee [8+8] Meeeeeeeeeeee ee Meeeeee eeee Meeeeee

Me e eeeeeee eeeeeee ee eeeeeeeeeeeee eeeeeeeee ee [8+8] eeeeeeeeeeeee ee e eeeeee eeee ee eeeeee, 8-eeeeeeeeeeeeeee eeeeeeee (‌888‌) ee eeeeeeeee eeee eee (8-eeeeeeeeeeee)eeeeee (‌888‌) ee eeeeeeeeeeeeeeeeeee eeee eeeeeeeeeeeee ee eeeeeeeee eeeeeeeeeee. Mee eeeeee eeeeee ee eeee eeee eee eeeeeeeeeeee ‌888‌ ee eeee eee eeee-eeeeeeeeeeeee ‌888‌ ee 88% eeeee eeee eeee eeee 88% eeeeeeeeeee eee eee eeee-eeeeee (‌Meeeee 88‌).[‌888‌] Me eeeeeeeee eeeeeeee ee eee eeeeeeee ee eeeeeeeeeeeeeeee eeeeeeee, eeeeeeeeeeeee eeeeee eeee eee eeeeeeeee ee ee ee 88% ee eee eee-eeeeee, eeeeeeeeee eeee eee eeeeee ee eee eeee eeeeee eeeeeee. Meee eeeeeeee eeeeeeee eeeeeeee ee e eeeeeeee eeeeeee, eeee eee eeeeeeeee ee e eeeeeeeeeeee eeeeeeeeeeee, eee e eeeeeeeee eeeeeee eeeeee ee eeeee eee.[‌888‌] Meeeeeeeeeee eee eeeeeeeeee eeeeeeeeee ee eeeeeeeeeeeee eeeeeeeee, eee eee eee ee eeeeeeeeeee (ee 88°M) ee eeeeeee eeeeeee e eeeeee eeeeeeee eeeeeeeeeee eee eeeee eeeeeeeeeeeeee eeeeeeee eeee eeeeee, eee eeeee eeeeeeee eeeeee eee eeeeee eeeeeeeeeeeeeeeeeee. Mee eeee eeeeeeee eeeeee(8-eeeeeeeeeeee)eeeeee eeeeeeeee eeeeeeeeeeeee ee eeee eeeeeeeeeee eee eeeee eee eeeeeeeeeeeee eeeeeee ee 88% eeeee (eee Meeeeee ‌88.8‌),[‌888‌] eeeee, eeeee Meeeee–Meeeeeee eeeeeeee, eee ee eeee eee eee eeeeeeeeeee ee eeeeeeeeeeeee.

‌Meeeee 88‌ Meeeeeeeeeeee Meeeeeeee eeee (8-Meeeeeeeeeee)eeeeee ee [8+8] Meeeeeeeeee eeee ee Meeeeeeeeeee[‌888‌]

Meeeeeeeeeeeeeee (‌888‌), eeeeee ee eeeeeeeeeeeee Meeee eeeeeeeeeeeee ee eee eeeee eeeeee ‌888‌ ee eeeeeeeeeeee, eeeee eee eeeeeeeeeeeeeeeeeee ‌888‌ (eeeeeeeeee eee eee-eeeeee) ee [8+8] eeeeeeeeeeeee eeee eee eeeeeeee eeeeee (‌Meeeee 88‌).[‌888‌] Meeee-eeeeeeeee eeeeeee eeeeeeeee ee ‌888‌ eee e eeeeeee ee eeeee eeeee eeeeeee eeee eeeee eeeee eeeee ee eee eeeeeee eeeeeee.[‌888‌]

‌Meeeee 88‌ Meeeeeeeeeeee Meeeeeeee ee [8+8] Meeeeeeeeeeee ee Meeeeeeeeeee eeee Meeeeeeeeeeeeeee eeee Meeee Meeeeeeeeeeee[‌888‌]

Meeeeeeeeeee Meeeeeeee

8-eeee-Meeeeeeeeeee[8.8.8]eeee-8-ee-8-eee (‌888‌, M8 = e-Me); Meeeeee Meeeeeeee:[‌88‌]

8,8-Meeeeeeeeeeeeeee eeeeeeee (88 e, 8.88 eee) ee eeeeeeeee eeeee (888 eM) eee eeeee ee e eeeeeee eeee ee Me8M (88 e, 8.8 eee) eee eeeeeeeeeeeeeee (88 e, 8 eee) ee eeeeeeeee eeeee (8 M). Mee eeeeeee eee eeeeeee eee 88 e ee 88°M eee eeee eeeeeeee. Meeeeeeeeee eeeeee (888 eM) eee 88% MeMM (888 eM) eeee eeeee, eee eee eeee eee eeeeee eee 8 e ee 888°M. Mee eeeeeee eee eeeeeeeee eeee Me8M, eee eee eeeeeeee eeee eeeeee eeee 8 M MeMM eee 8 M M8MM8, eeeeeeeeeeee, eee eeeeeeeee; eeeee: 8 e (88%); ee 88–88°M/88 Meee.

8-(Meeeeeeeeeeeeeeee)-8-(8-eeeeeeeeeeee)-8-eeeeeeeeee[8.8.8]eeeeee-8-eee (‌888‌); Meeeeee Meeeeeeee:[‌888‌]

M eeee ee 8-eeeeeeeeeeeeeee eeeeeeee (‌888‌; 8.88 eM, 8.8 eeee) ee eeeeeeeeeee (8.8 eM) eee eeeeee eeeee ee e eeeeeeeee eeee ee Me8M (8.88 eM, 8.8 eeee) eee eee eeeeeeeeeeee ‌888‌ (8.888 e, 8.88 eeee) ee eeeeeeeeeee (88 eM) ee eeeee e eeeeeee eeee eeee eee eee ee eee eeeeeee eeeeee eeeeeeee ee eee eeeeeeeee eeee. Mee eeeeeeeee eeee, eeeeeeeeee e eeee eeeeee eeeeeeeeee, eee eeeeeeee eee 8 e, eeeeee ee ee, eeeeeeee eeeeeee e eee ee Meeeee, eee eeeeeeeeeeee eeeee eeeeeee eeeeeeee. Mee eeeeeeeee eee eee eeeeeeeee ee MeMMe/eeeeee (8:8, 88 eM) eee eeeeeeeee eeee 88% MeMMM8 (88 eM) eee eeee M8M (88 eM). Mee eeeeeee eeeeeee eee eeeee (Me8MM8), eeeeeeee, eee eeeeeeeeeeee eeeee eeeeeee eeeeeeee ee eeee e eeeeee eee eeee eee eeeeeeeee ee eeeee eeeeeeeeeeeeee (eeeeee eee, MeMMe/eeeeee 8:8); eeeee: 8.888 e (88%).

References

Meeeeee Meeeeeeeeee

• 8.Meeeee-Meee, (8888) 8/8, 888.
• 8.Meeeee-Meee, (8888) M 88-8, 8888.
• 8.Meeeee-Meee, (8888) M 88e, 888.