Tf2O-Mediated Cyclization of α-Acyl-ß-(2-aminopyridinyl)acrylamides: Access to N-Substituted 4H-Pyrido[1,2-a]pyrimidin-4-imines.

A facile and efficient direct synthesis of N-substituted 4H-pyrido[1,2-a]pyrimidin-4-imines is developed from α-acyl-ß-(2-aminopyridinyl)acrylamides mediated by triflic anhydride (Tf2O) in the presence of 2-chloropyridine. This amide activation protocol features mild reaction conditions, simple execution, excellent yields, and high chemoselectivity, and is also applied to the synthesis of substituted 4H-pyrido[1,2-a]pyrimidin-4-ones via a practical one-pot procedure.

Oxidative Cyclization of ß-Aminoacrylamides Mediated by PhIO: Chemoselective Synthesis of Isoxazoles and 2 H-Azirines.

Cyclization of a variety of ß-aminoacrylamides in the presence of iodosobenzene (PhIO) is described. This process features mild reaction conditions, simple execution, and high chemoselectivity and thereby provides an efficient protocol for the divergent synthesis of substituted isoxazoles and 2 H-azirines via switchable N-O and N-C bond formation controlled by simply varying the ß-substituent R3 of the readily available substrates.

Iodosobenzene-Mediated α-Acyloxylation of 1,3-Dicarbonyl Compounds with Carboxylic Acids and Insight into the Reaction Mechanism.

A highly efficient direct α-acyloxylation of 1,3-dicarbonyl compounds with carboxylic acids mediated by hypervalent iodine reagent is presented. Treatment of a variety of 1,3-dicarbonyl compounds with carboxylic acids in the presence of iodosobenzene provides the corresponding α-acyloxylated products in good to excellent yields. The mechanistic investigation by means of NMR spectroscopy reveals that the in situ-generated phenyliodine biscarboxylate proves to be the key intermediate for the α-acyloxylation, and the loading sequence of reactants and oxidant is crucial for the generation of the active species. The mild reaction conditions, wide substrate scope, short reaction time, good yields, high chemoselectivity, excellent functional group tolerance, and metal catalyst-free conversion make this acyloxylation a significant synthetic protocol.

Direct Synthesis of Thioethers from Carboxylates and Thiols Catalyzed by FeCl3.

A new and efficient method has been developed for the synthesis of thioethers from carboxylates and thiols. The reaction proceeds via a Fe(III)-catalyzed direct displacement of carboxylates from benzylic or allylic esters by heterocyclic thiols. Short reaction times, good to excellent yields of products, and few side reactions are the significant features of the new protocol.

Isolation, structural assignment and synthesis of (SE)-2-methyloctyl 3-(4-methoxyphenyl) propenoate from the marine soft coral Sarcophyton ehrenbergi.

A new metabolite 1 has been isolated from the marine soft coral Sarcophyton ehrenbergi along with two known diterpenoids 2 and 3 and cholesterol 4. The structure of 1 was determined by means of detailed spectroscopic analysis and unambiguously confirmed to have the S configuration by the synthesis of both enantiomers using 4-benzyl-2-oxazolidinone auxiliaries. (S)- and (R)-1, 3 and some of the synthetic intermediates were evaluated for cytotoxic activity against human lung cancer (A549), prostate cancer (DU145), cervical cancer (HeLa) and breast cancer (MCF-7) cell lines in an in vitro bioassay.