Caiding Xu

A highly efficient and selective synthesis of lissoclinolide featuring hydrogen transfer hydrozirconation,trans-selective Pd-catalyzed cross coupling of alkenylzirconiums with 1,1-dibromoalkenes and Ag-catalyzed lactonization providing(Z)-γ-alkylidenebutenolides

Abstract An antibiotic lissoclinolide has been synthesized from propargyl alcohol in 9 steps and in 32% overall yield via (i) hydrogen transfer hydrozirconation of TBS-protected propargyl alcohol with i -BuZrCp 2 Cl, (ii) Pd-catalyzed trans -selective cross coupling of the hydrozirconation product with a key 1,1-dibromoalkene intermediate 5 and (iii) Ag-catalyzed lactonization of a trienynoic acid precursor 2 .

Catalytic and selective conversion of (Z)-2-en-4-ynoic acids to either 2H-pyran-2-ones in the presence of ZnBr2 or (Z)-5-alkylidenefuran-2(5H)-ones in the presence of Ag2CO3

Abstract Treatment of (Z)-5-alkyl-2-en-4-ynoic acids ( 1 ), prepared by the Pd-catalyzed alkynylzinc–β-haloacrylic acid coupling, with 5–10 mol% of ZnBr2 can produce 6-alkyl-2H-pyran-2-ones ( 2 ) along with minor amounts of (Z)-5-alkylidenefuran-2(5H)-ones ( 3 ) in >90% combined yields, with often very high (≈95/5) pyranone/furanone ratios. On the other hand, lactonization of 1 catalyzed by Ag2CO3 provides a selective synthesis of (Z)-5-alkylidenefuran-2(5H)-ones ( 3 ) in >90% yields along with minor amounts (≤5%) of 2 .

Intermolecular trapping of acylpalladium and related acylmetal derivatives with active C-H compounds

Abstract The reaction of aryl and alkenyl iodides and bromides with highly acidic ketones in the presence of CO (40–45 atm), NEt3 (1–2 equiv.), and 5 mol% of Cl2Pd(PPh3)2 in DMF at 100°C provides the corresponding enol carboxylates formed via trapping of putative acylpalladiums with O-enolates. In cases where alkenyl halides are used, the initially formed products can cyclize to give the corresponding lactones.

A general method for the synthesis of E and/or Z oligoisoprenoids based on Pd-catalyzed homoallyl-alkenyl and homopropargyl-alkenyl cross coupling and Zr-catalyzed carboalumination

A truly general, versatile, and highly regioselective and stereoselective methodology for the synthesis of terpenoids containing 1,5-diene units of E and/or Z geometry critically involves (a) Pd-catalyzed homoallyl-alkenyl and homopropargyl-alkenyl coupling and (b) Zr-catalyzed carboalumination of alkynes. In each introduction of an E or Z trisubstituted C5 alkene unit, the yield is excellent, and the regioselectivity and stereoselectivity level is >98%. As such, this appears to represent the first general synthetic method accommodating Z alkene units in >95% regioselectivity and stereoselectivity. Its application to some representative terpenoids of both natural and unnatural geometries is discussed.