An efficient method to synthesis the 2H-pyrans using three component reactions of dithiocarbamats, activated acetylenes and isocyanides in water as the solvent is described. In these reactions, synthesis of 2H-pyrans is possible based on the one-pot reaction and without using any catalyst. The mild reaction conditions and high yields of the products exhibit synthetic advantage of these methods.

Novel, highly coloured benzopentalenonaphthalenones result from a cascade process initiated by the thermally-induced ring-opening of diarylmethanol substituted 2H-naphtho[1,2-b]pyrans in the presence of acid.

Asymmetric allylic alkylation is a powerful reaction that allows the enantioselective formation of C-C bonds. Here we describe the asymmetric alkylation of alkylzirconium species to racemic 3,6-dihydro-2H-pyrans. Two systems were examined: 3-chloro-3,6-dihydro-2H-pyran using linear optimization (45-93% ee, up to 33% yield, 5 examples) and 3,6-dihydro-2H-pyran-3-yl diethyl phosphate with the ass...

To the article ''Thia-Diels–Alder reactions of hetaryl thioketones with nonactivated 1,3-dienes leading to 3,6-dihydro-2H-pyrans: evidence for a diradical mechanism'' by Grzegorz Mlostoń, Paulina Grzelak, Anthony Linden, Heinz Heimgartner

2-Sulfonimidoylylidene tetrahydrofurans and 5-vinyl-2-sulfonimidoylylidene tetrahydrofurans were readily synthesized via a consecutive acylation/SN2 sequence with total regioand chemoselectivity from Johnson’s sulfoximine derivatives. The same consecutive reaction could also be applied to the expeditious synthesis of 6-sulfonimidoylmethyl-3,4-dihydro-2H-pyrans. © 2012 Elsevier Science. All righ...

The highly enantioselective dienamine-mediated formation of 5-bromo-6-(trifluoromethyl)-3,4-dihydro-2H-pyrans from α,β-unsaturated aldehydes and α-bromo-(trifluoromethyl)-enones employing a C2-symmetric aminocatalyst is described. The products are demonstrated to be applicable in coupling reactions directly onto the ring, thereby granting access to a broad scope of highly substituted 6-(trifluo...

The 1,6-conjugate addition of nucleophiles to dienyl diketones produces either cyclopentenone or 2H-pyran products with high selectivity through either Nazarov (4π) or 6π electrocyclization, respectively. The outcome of the reaction is dependent upon the nature of the nucleophile used. Nucleophiles that are anionic or easily deprotonated exclusively produce cyclopentenones via Nazarov cyclizati...

The carbene complex 5-(2,2-dimethyl-2H-chromene)methoxylmethylene chromium pentacarbonyl will undergo a benzannulation reaction with phenylacetylene, 1-pentyne, 3-hexyne, and trimethylsilylacetylene to give 7-hydroxy-10-methoxy-3H-naphtho[2.1-b]pyrans as the primary product. These compounds are difficult to obtain pure due to their sensitivity to air. If the benzannulation reaction is performed...