Bicyclo[m.n.1]alkenone frameworks possessing quaternary carbon centers adjacent to a bridged ketone are frequently found in bioactive natural products. Although several methods have been developed to construct such frameworks, most of them are specific to a particular scaffold. Herein, we report a mild and highly efficient method to generate carbon-bridged frameworks of various sizes using phosphino gold(I) catalysts.

We have developed an innovative strategy for the formation of angular carbocycles via a gold(I)-catalyzed dehydro Diels-Alder reaction. This transformation provides rapid access to a variety of complex angular cores in excellent diastereoselectivities and high yields. The usefulness of this Au -catalyzed cycloaddition was further demonstrated by accomplishing a 11-steps total synthesis of (±)-magellanine.

For many years, despite a rich coordination chemistry, gold (Au) was judged as being catalytically inactive for the formation of carbon–carbon bonds. In mid-1970, few reports demonstrated that Au salts could be very useful reagents to catalyze organic transformations. In recent years, homogeneous catalysis by Au has received considerable attention by the scientific community. It was shown that Au(I) or (III) catalysts are specific and more reactive than most of the other soft Lewis acids such as Hg(II), Cu(II), Pt(II), and Pd(II). Taking advantage of the affinity of cationic phosphine Au complexes to triple bonds, we conceived a Au(I)-catalyzed 6-endo-dig cyclization of cyclic enol ether to prepare bridged and fused bicyclic ketone. Keeping in mind that 5-exo-dig cyclizations can be a competitive process, we surveyed various Au(I) complexes.

We have developed an innovative strategy for the formation of angular carbocycles via ag old(I)-catalyzed dehydro Diels-Alder reaction. This transformation provides rapid access to avariety of complex angular cores in excellent diastereoselectivities and high yields.T he usefulness of this Au I -catalyzed cycloaddition was further demonstrated by accomplishing a1 1-steps total synthesis of (AE)-magellanine. Scheme 3. Total synthesis of magellanine 7.Reagents and conditions: a) TMAD, TBP, 19, o-xylene, 0 8 8C; then BHT 150 8 8C. b) OsO 4 ,NMO, NaIO 4 , THF:H 2 O, 20 8 8C. c) Piperidine, AcOH, PhMe, 20 8 8C. d) TIPSOTf, DMS, LiHMDS, THF, À78 8 8C. e) [L6AuNCMe][SbF 6 ](1mol %) PhMe, 20 8 8C; then CSA (1 equiv). f) TBAF, 60 8 8C; then LiOH, H 2 O/THF, 140 8 8C. g) DMP, DCM, 20 8 8C. h) PtO 2 ,H 2 ,E tOAc, 20 8 8C. i) i-PrCO 2 Cl, NMM, Et 3 N, 25,P hMe, 0 8 8C; then 365 nm LED, O 2 , tert-dodecylmercaptan, 0 8 8C; then PPh 3 .j )DIAD, HCO 2 HPPh 3 ,THF;then LiOH. k) Na, naphthalene, THF, À78 8 8C; then AcOH, formaldehyde, NaBH 3 CN, 20 8 8C. l) LDA (2 equiv),T MSCl (1 equiv), 30,THF, 0 8 8C; then HCl, 20 8 8C. TMAD = tetramethyl azodicarboxamide, TBP = tributylphosphine, BHT = butylated hydroxytoluene, NMO = N-methylmorpholine N-oxyde, THF = tetrahydrofuran, TIP-S = triisopropylsilyl, DMS = dimethyl sulfide, CSA = camphorsulfonic acid, TBAF = tetrabutylammonium fluoride, DMP = Dess-Martin periodinane, DCM = dichloromethane, NMM = N-methylmorpholine, DIAD = diisopropyl azodicarboxylate, LDA = lithium diisopropylamide, TMS = trimethylsilyl.

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