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1.3.1.3.1.2 Enyne Ring-Closing Metathesis for Small Rings

DOI: 10.1055/sos-SD-219-00067

Lee, D.; O'Connor, M.Science of Synthesis: Applications of Domino Transformations in Organic Synthesis, (2015192.

Due to their strained nature, small-sized rings containing unsaturation usually undergo ring-opening metathesis; therefore, their formation by ring-closing metathesis is quite challenging under inherently reversible metathesis conditions. Contrary to this general notion, it has been demonstrated that cyclobutenes can be generated from 1,5-enynes via enyne ring-closing metathesis.[‌76‌] This unusual ring-closing metathesis subsequently inspired the ring-closing metathesis of 1,5-enyne 71 using the Hoveyda–Grubbs second-generation ruthenium alkylidene complex 7 under microwave irradiation to generate 72 in high yield [83%; an alternative procedure not employing microwave irradiation affords the product in lower yield (66%)]. This product is elaborated to (±)-grandisol via chemo- and stereoselective hydrogenation followed by deprotection of the silyl group (Scheme 24).[‌77‌]

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Meeeee 88 Meeeeeeee ee Meeeeeeeeee[‌88‌]

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M8 Meeee (%) ee 88 Mee
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MMe >88 [‌88‌]
MMMMMM >8 [‌88‌]
M >88 [‌88‌]

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References


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