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Please login or sign up for a free trial to access the full content. Method 23: Alkene Metathesis

DOI: 10.1055/sos-SD-026-00987

Marsden, S. P.Science of Synthesis, (2005261104.

Alkene metathesis, both in ring-closing and cross-metathesis modes, is one of the pre-eminent methods for alkene formation in modern chemistry. In terms of enone synthesis, the broad lack of compatibility of ketone functionalities with the first generations of metathesis catalysts such as 348 meant that this reaction was extremely substrate specific in terms of success (Scheme 61). The advent of more electron-rich ruthenium catalysts such as 349 and 350 bearing dihydroimidazolenyl ligands has opened up this new area. Alkene cross metathesis is highly successful for enones, as demonstrated by the highly efficient, highly trans-selective formation of 353 from 351 and 352.[‌268‌] The success of this reaction is due in part to the reluctance of enones to undergo self-metathesis, although this can be achieved under carefully controlled conditions, yielding enediones.[‌269‌] Ring-closing metathesis is a more facile process and high yields of enones can be generated from acyclic dienones such as 354.[‌268‌] The ring-closing reaction is particularly useful in synthesis, for example in the formation of unusual spirocyclic enones 355.[‌270‌] The use of tandem metathesis sequences also allows for the construction of polycyclic enones such as 357 from relatively simple precursors, e.g. 356.[‌271‌]

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