The chamigrene subclass of sesquiterpenes, characterized by a spiro[5.5]undecane core, is an ever-growing family of natural products (Figure 1). 1 Well over one hundred members have been isolated thus far, and many of these compounds exhibit a diverse array of biological activity. 1c In particular, elatol (1), 2 one of the most widely studied chamigrenes, displays antibiofouling activity, 3a-b antibacterial activity (including human pathogenic bacteria), 3c-e antifungal activity, 3f and cytotoxicity against HeLa and Hep-2 human carcinoma cell lines. 3g Despite the interesting bioactivity and compact structure of these molecules, no general strategy for their preparation has been developed, and, to the best of our knowledge, no total synthesis of elatol has been reported in the thirty-three years since its original isolation. 4,5Structurally, elatol (1) consists of a densely functionalized A ring bearing three stereocenters, including an all-carbon quaternary stereocenter, which is vicinal to a second, non-stereogenic quaternary carbon. Within the B ring is also a fully substituted chlorinated olefin. We envisioned a strategy toward these challenging motifs based on methodological advances recently reported by our laboratories. Specifically, enantioselective decarboxylative allylation 6 could generate the all-carbon quaternary stereocenter, while ring-closing metathesis (RCM) 7 could be employed to concomitantly provide the tetrasubstituted olefin and the spirocyclic core of 1 (Scheme 1). Importantly, this approach serves as a general platform to access the chamigrene family.We envisioned 1 to ultimately arise from sequential reductive olefin transposition and diastereoselective reduction of α-bromoketone 10. In turn, compound 10 would be obtained from bromination of the enone resulting from 1,2-addition of a methyl anion to spirocycle 11. Intermediate 11 itself could be the product of RCM of α,ω-diene 12. Although generation of a fully substituted chlorinated olefin via RCM has not been previously reported, 8 we anticipated that the improved reactivity of catalyst 22 7 (vide infra) might be sufficient for this transformation. Access to 12 would be possible via enantioselective decarboxylative allylation of an appropriately substituted vinylogous ester derivative (i.e., 13), employing the Pd(0) complex of a phosphinooxazoline (PHOX) ligand. This would constitute a previously unexplored substrate class with this catalyst system. 9 Finally, enol carbonate 13 could be derived from commercially available dimedone (14).Our synthetic efforts began with the condensation of isobutyl alcohol and dimedone (14) to provide known vinylogous ester 15 (Scheme 2). 10 Direct alkylation of vinylogous ester 15 with 4-iodo-2-methyl-1-butene was sluggish; however, a two-step procedure involving conjugate addition to methyl vinyl ketone (MVK) followed by Wittig methylenation afforded olefin (±)-16 in good yield. Selective enolization of vinylogous ester (±)-16 and trapping with chloroformate 17 allowed access to enol carbonate 13 in 7...