Serendipitous and acid catalyzed synthesis of spirolactones

Synthetic Approach toward Diverse Oxa-Cages via Olefin Metathesis

“…Reports are available, where cycloetherification was initiated by using the additive (acid or base), despite the presence of severe ring strain (Figure ). Herein, a domino attack of allylmagnesium bromide, i.e., nucleophilic addition followed by cycloetherification without any additive (acid or base), an intricate oxa-cage system was produced. To this end, we concluded that the convex face of the bridged bicyclic system and carbonyl groups of 22 are in a favorable orientation for cycloetherification.…”

Structure determination from X-ray powder diffraction, DFT calculation, and Hirshfeld surface analysis of two fused bicyclic and tricyclic compounds

“…The relative contribution of different interactions to the Hirshfeld surfaces of 1, 2 and a few fused 6, 5 cyclic systems retrieved from the CSD are shown in Figure 7. It is evident from Figure 7 that H ⋯ H and O ⋯ H interactions can account for about 85% of the Hirshfeld surface area, 85.7% in 1 and 83.7% in 2 , whereas the corresponding values for 3′-(2-hydroxypropyl)-5-methyldihydro-4′H-spiro[furan-3,2′-[5]oxatricyclo[4.2.1.0 3,7 ]nonane]-2,4′-dione (OTAKOK) (Kotha et al ., 2011) and 3′-isopropyl-7a′-methylhexahydrospiro[[1,3]dioxolane-2,5′-inden]-1′(6′H)-one (XIMJEK) (Hog et al ., 2012) are 98.4 and 99.7%, respectively. An approximately twofold decrease in the contribution of O ⋯ H contacts from 33.3% in 1 to 18.7% in 2 is a consequence of reduced percentage of oxygen atoms in the molecular formula of 2 (4.4%) in comparison with that in 1 (12.8%).…”

Design and Synthesis of Spirocycles

“…H 2 SO 4 gave bis‐lactone 153 in 65 % yield. On another occasion, compound 154 was obtained in 78 % yield by starting from 36a (Scheme ) . The structures of 153 and 154 were confirmed by single‐crystal X‐ray diffraction studies.…”