An efficient asymmetric approach to access functionalized pyrido-and pyrrolo[1,2-c][1,3]oxazin-1-ones has been developed through a nucleophilic addition−cyclization process of N,O-acetal with ynamides. A number of substituted ynamides 8a−8o and 3silyloxypyrrolidine or piperidine N,O-acetals 6a, 7 were amenable to this transformation, and the desired products 9a−9o, 10a−10m were obtained with excellent regioselectivities and outstanding diastereoselectivities. Moreover, chiral ynamides 14a−14f could also experience this addition−cyclization process to afford products 15a− 15f in excellent yields. Article pubs.acs.org/joc

An efficient and mild zinc-mediated decarboxylative alkylation of gem-difluoroalkenes with N-hydroxyphthalimide (NHP) esters, to give monofluoroalkenes in moderate to excellent yields with high Z-selectivity is reported. The reaction tolerates a broad range of functional groups and can be easily scaled up, which thus may pave the way for its further applications in medicinal chemistry and materials science.

Dolastatin 10, an antineoplastic agent for cancer chemotherapy, is a linear peptide possessing N,N-dimethyl Val-OH, l-valine, (3R,4S,5S)-dolaisoleucine, (2R,3R,4S)-dolaproine and (S)-dolaphenine. Our efficient synthesis includes the following three key features: (1) SmI-induced cross-coupling was employed to couple aldehyde 11 with (S)-N-tert-butanesulfinyl imine 12 to generate the required stereocenters of Dap (7); (2) asymmetric addition of chiral N-sulfinyl imine 10 provided a straightforward approach to the synthesis of the protected Doe ((S,S)-8); (3) a practical method to the key subunit Val-Dil (24a) has been established as an alternative synthetic route for the synthesis of this challenging chemical structure.

A diastereoselective one-pot approach to access trans-5-hydroxy-6-substituted-2-piperidinones by an addition-cyclization-deprotection process has been developed, in which the stereogenic center at the C-6 position was solely controlled by α-OTBS group. The utility of this transformation is demonstrated by the asymmetric synthesis of the enantiomer of (-)-CP-99,994.

A palladium-catalysed method for intramolecular cyclisation of ortho-diazonium salts of diaryl ethers to give dibenzofurans is described. The protocol uses 3 mol% palladium acetate as the catalyst in refluxing ethanol in the absence of base.