No abstract

The photocatalytic oxidation of a furan to a hydroxybutenolide in good yield is the first step of a one-pot synthesis of a g-substituted a,b-unsaturated g-butyrolactone in the ionic liquid 1-hexyl-3-methylimidazolium chloride ([HMIM] [Cl]).

An efficient preparation of a cholesterol analogue possessing a triazole ring is achieved starting from commercially available stigmasterol. The procedure is based on a [3+2] cycloaddition of a cholesterol possessing a side-chain terminal azide with a terminal acetylene.

Key indicators: single-crystal X-ray study; T = 293 K; mean (C-C) = 0.004 Å; R factor = 0.048; wR factor = 0.152; data-to-parameter ratio = 16.6.The chiral title compound, C 19 H 32 O 2 , contains a [4.3.0]-bicyclic moiety in which the shared C-C bond presents a trans configuration and a side chain in which the C C double bond shows an E conformation. The conformations of fiveand six-membered rings are envelope (with the bridgehead atom bearing the methyl substituent as the flap) and chair, respectively, with a dihedral angle of 4.08 (17) between the idealized planes of the rings. In the crystal, the molecules are self-assembled via classical O-HÁ Á ÁO hydrogen bonds, forming chains along [112]; these chains are linked by weak non-classical C-HÁ Á ÁO hydrogen bonds, giving a twodimensional supramolecular structure parallel to (010). The absolute configuration was established according to the configuration of the starting material.