[reaction: see text] A diastereoselective tandem Stille-oxa-electrocyclization reaction provides access to the core of the diterpenoid natural product saudin. Additionally, this new reaction sequence was extended to the convergent preparation of related polycyclic pyran systems.

Pyran (copolymer of divinyl ether and maleic anhydride) and tilorone [2,7-bis(2-diethylaminoethoxy) fluoren-9-one dihydrochloride] are host resistance-inducing agents that possess antitumor activity. The possible relationship of direct cytotoxicity to antitumor activity against the Lewis lung carcinoma and B-16 melanoma tumors was examined. Tilorone and tilorone congeners exhibited significant ...

In the title compound, C(23)H(24)N(2)O(7), the central 4H-pyran ring adopts a flattened boat conformation, whereas both cyclo-hexenone rings adopt envelope conformations, the C atom bearing the dimethyl substituent being the flap atom in each case. The mean and maximum deviation of the pyran ring are 0.0379 (4) and 0.0605 (3) Å. The mean plane of the pyran ring and the dinitro-benzene ring make...

The title compound, C15H14Br2O4 [systematic name: rac-(9S,10R)-3,9-dibromo-10-methoxy-8,8-dimethyl-9,10-dihydropyrano[2,3-h]chromen-2(8H)-one], is a pyran-ocoumarin derivative formed by the bromination of seselin, which is a naturally occurring angular pyran-ocoumarin isolated from the Indian herb Trachyspermum stictocarpum. In the mol-ecule, the benzo-pyran ring system is essentially planar, w...

An easy, effective and eco-friendly one-pot process for the preparation of 4H-pyran compounds has been established by using a catalytic amount reduced graphene oxide functionalized with diethylenetriamine (rGO-DETA) in water under mild conditions. The catalyst was very this reaction provided desired products 1a–t good to high yields (87%–97%) short times. Moreover, rGO-DETA composite could be r...

nano tin dioxide was employed as a catalyst for efficient and facile preparation of pyran derivatives via the one-pot three component condensation reaction of various aldehydes with malononitrile and dimedone. chromene derivatives via the one-pot three component condensation reaction of various aldehyde with malononitrile and 4-hydroxycoumarin were also synthesized by this novel catalyst. the d...

A new class of N-annulated perylene tetraesters and their N-alkylated derivatives has been synthesized. N-Annulated perylene tetraesters stabilize a hexagonal columnar phase over a broad temperature range. The hexagonal columnar phase exhibited by these compounds shows good homeotropic alignment with few defects. Annulation in the bay region of the perylene tetraesters enhanced the width of the...

An atom-economic synthetic route to benzimidazolium salts is presented. The annulated polycyclic systems: 1,3-bis(2,4,6-trimethylphenyl)-1H-benzo[d]imidazol-3-ium chloride (1-Cl), 1,3-bis(2,6-diisopropylphenyl)-1H-benzo[d]imidazol-3-ium chloride (2-Cl), 1,3-diphenyl-1H-benzo[d]imidazol-3-ium chloride (3-Cl), and 1,3-di(pyridin-2-yl)-1H-benzo[d]imidazol-3-ium chloride (4-Cl) were prepared in a t...

Theoretical calculations were carried out to understand the effect of annulation on the electronic and ligand properties of boron substituted N-heterocyclic carbenes (B-NHCs). Annulation results in a decrease in stability as indicated by the calculated values of singlet-triplet separations and stabilization energies as well as HOMO-LUMO gaps. Annulated B-NHCs are found to be weaker σ-donors but...

Driven by the shortage of known effective possibilities for the synthesis of 4-hydroxy-3,4-dihydro-2H-1,3-thiazine-2-thiones on the one hand and the promising potential of these structures as novel drug candidates on the other hand, synthetic access to 4-hydroxy-3,4-dihydro-2H-1,3-thiazine-2-thiones was developed. The desired products could be synthesized effectively and facilely starting from ...