An efficient copper-promoted hydration reaction and its application in the synthesis of benzo[b]furan and benzo[b]thiophene derivatives is presented starting from readily available 2-fluorophenylacetylene derivatives. The key annulation step involves the hydration of the C-F bond of 2-fluorophenylacetylene derivatives followed by an intramolecular annulation to afford benzo[b]furan and benzo[b]...

The annuloselectivity in the reactions of methanesulfonyl sulfene and imines varies with temperature. At a relatively higher temperature of 20 °C, the [2(s) + 2(i)] annulation of different N-alkyl imines occurs exclusively, giving four-membered trans-β-sultams in up to 69% yields. At a lower temperature of -78 °C, the [2(s) + 2(i) + 2(i)] annulation of N-methyl imines takes place specifically, ...

Sexannulate Orobdella leech, Orobdella ijimai, is redescribed based on newly collected specimens from the type locality, Nikko, Tochigi Pref., Japan, since this species was originally described based on limited number of characters. In addition, two new sexannulate species, Orobdella dolichopharynx sp. nov. from Amamioshima Island in the Ryukyu Archipelago, Japan, and Orobdella shimadae sp. nov...

The Pd(TFA)2-catalyzed [4+1] annulation of chained or cyclic α-alkenyl-dicarbonyl compounds and unprotected primary amines for “one-pot” synthesis of pyrroles is reported here. Enamination and amino-alkene were involved in this practical and efficient tandem reaction. The annulation products were isolated in moderate to excellent yields with O2 as the terminal oxidant under mild conditions. In ...

The protecting-group-free asymmetric synthesis of 1,2,4-trideoxy-1,4-imino-L-xylitol is readily achieved in five steps from 2-deoxy-D-ribose and with an overall yield of 48%. Key in this synthesis is the application of our recently developed Vasella-reductive amination and carbamate annulation methodologies to the synthesis of 2-deoxy-aza-sugars. The carbamate annulation occurred with excellent...

A series of benzo-annulated rutaecarpines were prepared from anthranilic acid and 3-aminonaphthalene-2-carboxylic acid by Fischer indole synthesis as key reaction. Cytotoxicity was somewhat increased by the introduction of benzo-annulation, which was not directly related to the inhibitory activity against topoisomerases (topo) I and II. Benzo-annulation on ring A led to significant increase of ...

Cu(I)-mediated annulation reaction of a 1,1'-(1,3-butadiyne)-8,8'-(2,5-thiophene)-bridged carbazole dimer 10 with amines provided the N-substituted carbazole-based isophlorines 11a-11c. A similar annulation reaction with selenium in the presence of hydrazine monohydrate afforded hetero-core-modified isophlorine 12. The oxidation of 12 generated the corresponding 21-selena-23-thiaporphyrin 13, w...

A sequential Diels-Alder reaction/silicon-directed [4 + 2]-annulation was developed to assemble hydroisochromene-type ring systems from menadione 2. In the first step, a Diels-Alder of the 1-silyl-substituted butadiene 1 with 2 furnished an intermediate cyclic allylsilane. Subsequently, TMSOTf promoted a [4 + 2]-annulation through trapping of an oxonium, generated by condensation between an ald...

The annulation reaction between various indoles and 2-alkoxycyclopropanoate esters is reported. Both high efficiency and complete stereochemical control were observed in some cases with this annulation process. A single stereocenter on the cyclopropane controls the diastereoselective formation of up to four new stereocenters. A different reaction course was observed with 3-substituted indole su...

Part I: The synthesis of 2-vinylindole, the parent of 2-alkenylindoles, has been achieved in three steps (70-76% yield) based on a novel allene cyclization developed in our laboratory. 2-Alkenylindoles have found use as precursors to indole and carbazole alkaloids via the Diels-Alder reaction. The key step of the synthesis involves isomerization of an arylacetylenecarbamate to an arylallenecarb...