An unusual case of Khand-Pauson cyclization involving the participation of a conjugated double bond. A promising sequence for the assemblage of polycyclic framework

Synthetic Approaches to Crinipellin Based Tetraquinanes via Ring‐Rearrangement Metathesis and Ring‐Closing Metathesis

“…At the conclusion of the reaction (by TLC monitoring), an ice-cold aqueous saturated NH 4 Cl solution (5-20 mL) followed by water (5-20 mL) was added to RM and the resultant solvent mixture was extracted with EtOAc (3 × 20-50 mL). The organics were evaporated and the resulting crude product was purified by column chromatography using an appropriate mixture (EtOAc/PE) as an eluent to afford the corresponding methyl product (14,15,23,24) as a colourless liquid. 3065,2957,2926,2854,1738,1640,1462,1456,1422,1376,1284,1260,1170,1094,1082,1027,914,837,804,758, 713 cm À 1 .…”

“…After the isolation of tetraquinane from Nature, several groups reported the synthesis of tetraquinane skeleton and total synthesis of various crinipellins and their derivatives. Selected groups include: Mehta, [13] Curran, [14] Veretenov, [15] Piers, [12,16] Moore, [17] Wender, [18] Paquette, [19] Srikrishna, [20] Lee, [21] Kotha, [22] Yang, [23] etc. However, only a few reports were found with metathetic approaches [2c,22,24] …”

Application of Pauson–Khand reaction in the total synthesis of terpenes

“…Therefore, IPKR has found several applications in the total synthesis of natural products frequently used as the key step. 6,[24][25][26] Synthetic organic chemistry has developed momentously owing to the exponential growth in transition-metal-catalyzed reactions. The effect of transition-metal-catalyzed reactions on organic synthesis could be evaluated by the wide range of molecules that have been developed from simple compounds to complex natural products.…”

Selected Synthetic Strategies to Spirocyclics

“…For example, this IMPK approach was used to synthesize tetracyclic product 360 (Scheme 97), a precursor to the diterpene crinimpellin A (9; Figure 2). 113 In this reaction, 360 was obtained in 73% yield when the cyclization took place upon thermolysis of 359 in a diethyl etherpentane solution.…”