Cyclopenta[c]pyrans from 6-oxo-6H-1,3,4-oxadiazines†

Indenopyrans – synthesis and photoluminescence properties

“…The cycloaddition reaction proceeded with moderate regio- and stereoselectivity. As reported in the literature, the inverse-electron demand Diels–Alder cycloaddition of unsymmetrical olefins and oxadiazinones [ 33 – 35 ] may lead to two possible regioisomers: isomer 2 with the benzene ring fused at C5a–C9a and its regioisomer 3 with the benzene ring fused at C4b–C8a ( Fig. 1 ).…”

(3-Chlorophenyl){2-ethoxy-5-[(Z)-hydroxy(phenyl)methylidene]cyclopenta-1,3-dien-1-yl}methanone

“…The title compound was obtained as a by-product in the oxidation reaction of dihydro-α-pyrone 1-(3-chlorophenyl)-4phenyl-4a,5-dihydrocyclopenta[c]pyran-3(4H)-one with DDQ (2,3-dichloro-5,6-dicyano-1,4-benzoquinone) in chloroform (Christl et al 1998). We observed that during the dehydrogenation process in order to obtain the corresponding αpyrone, a competitive reaction underwent with formation of the fulvene derivative ( Fig.…”

“…For more information on the synthesis of 2-acyl-6-hydoxyfulvene derivatives, see: Dong et al (2004Dong et al ( , 2006. For preparation details, see: Christl et al (1998). For compounds obtained from 2-acyl-6-hydoxyfulvenes, see: Dong et al (2004); Li et al (2008); Snyder et al (2005).…”

Cyclopenta[c]pyrans

“…A general procedure of synthesis could not be elaborated yet, but several strategies starting from cyclopentadienes [41], fulvenes [42], oxadiazinones [4], and α‐pyrones [3] have been developed for the preparation of the parent compound 1 and derivatives with various substitution patterns.…”

“…This similarity suggests an analogy of the properties with those of azulene, foreshadowing the chemical behavior of the cyclopenta[ c ]pyran entity. However, there are only few reports dealing with the reactivity of cyclopenta[ c ]pyrans [3, 4], showing strong preference of the electrophilic attack at 7‐ and 5‐positions.…”