Science of Synthesis

Koo, S., Science of Synthesis, (2010) 45, 1402.

The palladium-catalyzed [3 + 2 + 2] cycloaddition of one molecule of 2-substituted allylic alcohols ‌185‌ and two molecules of alkynes ‌186‌ produces pentasubstituted cycloheptatrienes ‌187‌ and ‌188‌ (‌Scheme 41‌).[‌183‌] The selectivity between ‌187‌ and ‌188‌ is moderate in most cases and not significantly affected by the reaction conditions. The cycloaddition reaction proceeds via an (η3-allyl)palladium intermediate ‌189‌. Successive insertion of two molecules of symmetrical alkynes ‌186‌, followed by a 7-endo-trig cyclization affords cycloheptatrienes. The 2-R1 substituent of allylic alcohols ‌185‌ is very important in directing the cyclization toward a seven-membered ring formation. The cycloaddition reaction of allylic 4-toluenesulfonate (R1 = H) and hex-3-yne under similar conditions produces 1,2,3,4-tetraethyl-5-methylbenzene, in which the 6-exo-trig cyclization prevails.[‌184‌] No cyclization products can be obtained for certain alkynes such as diphenylacetylene, dibenzoylacetylene, dimethyl acetylenedicarboxylate, 1,4-dimethoxybut-2-yne, and several terminal alkynes.

‌Meeeee 88‌ Meeeeeeee-Meeeeeee [8 + 8 + 8] Meeeeeeeeeeee Me Meee Meeeeeeeeeeeeeeee[‌888‌]

‌Meeeeeeeeee 88‌

e Meeeeeeeee ee 8M MMM eeeeeeeeeeee.

e Meeeeeee eeeee.

e MM eeeee.

Meeeeeeeeeee Meeeeeeee

8,8,8,8-Meeeeeeeee-8-eeeeeeeeeeeeeeee-8,8,8-eeeeee (‌888‌, M8 = Me; M8 = Me) eee 8,8,8,8-Meeeeeeeee-8-eeeeeeeeeeeeeeee-8,8,8-eeeeee (‌888‌, M8 = Me; M8 = Me); Meeeeee Meeeeeeee:[‌888‌]

Me e eeee ee Me8(eee)8•MMMe8 (8.88 eeee, 88 ee), (8-Mee)8M (8.88 eeee, 888 ee), eee MeMM (8.88 eeee, 88 ee) ee 8,8-eeeeeeeeeeeeee (8 eM) eee eeeee 8-eeeeeeeeee-8-ee-8-ee (‌888‌, M8 = Me; 8.88 eeee, 88 ee) eeeee M8 ee e eeeeeeee eeee. Meeee eeeeeeee eee 88 eee, eee-8-eee (‌888‌, M8 = Me; 8.8 eeee, 8.88 eM) eee eeeee ee eee eeeeeee. Meeee eeeeeee ee 88°M eee 88 e, eee eeeeeee eee eeeeeeee eeeeeee e eeeee eeee (eeeeee eee, Me8M). Mee eeeeeeeee eeee eeeeeee eee eee eeeeeee eee eeeeeeee ee eeeeee eeeeeeeeeeeeee (eeeeee eee, eeeeee); eeeee: 88 ee (88%); eeeee (‌888‌/‌888‌) 8:8; eee eeeeeeee eee ee eeeeeeeee ee eeeee eeeeeeeeeeeeee.

References