Design and Synthesis of Highly Decorated Oxa‐Cage Systems via Olefin Metathesis

Abstract

Here, we report diversely fused oxa‐cages starting from various alkyl‐substituted cyclic‐ether derivatives derived via intramolecular cyclocetherification of endo‐alcohol containing endo‐norbornene derivatives. All these higher oxa‐cage systems are assembled in good to excellent yield by employing ring‐closing metathesis (RCM) or ring‐opening metathesis (ROM) as a key step. Ru‐based Grubbs catalysts (G‐I, G‐II) are effective to assemble these target molecules. In addition, a highly strained bicyclo[2.2.1]hepatane system fused oxa‐cages are easily prepared by hydrogenation sequence. Also, several highly fused saturated oxa‐cage derivatives are reported. A total of 22 examples are reported and all of these compounds are well‐characterized by NMR and HRMS data. The target compounds reported here may find significant applications in various fields of chemistry.

Synthetic Studies to Fused 5/5/6‐Tricyclic Frameworks: Access to Presilphiperfolanol Analogues and A, B, C‐Ring System of Lycopodium Alkaloids and Cyclopiane Diterpenes

“…Along similar lines, compounds 34 and 35 were identified and confirmed by NMR spectral data [26] . The 1 H NMR spectral data comparison of compounds 25 , 30 , and 31 is shown in Figure 7 [26] . Similarly, the 1 H NMR comparison of compounds 26 , 34 , and 35 are shown in Figure 8> [26] …”

“…However, these products are not realized in any instance. Instead, a mixture of cyclic ether 30 & RCM product 31 (yield of mixture 91 %), 34 & 35 (yield of mixture 88 %), and 38 & 39 (yield of mixture 93 %) were obtained in good yields [26] . Here, we could not separate compounds 30 & 31 by traditional column chromatography.…”

“…The 1 H NMR spectral data comparison of compounds 25 , 30 , and 31 is shown in Figure 7 [26] . Similarly, the 1 H NMR comparison of compounds 26 , 34 , and 35 are shown in Figure 8> [26] …”

“…Here, the keto compounds 11 and 12 are derived from tricyclic ketone 10 by an alkylation sequence (Scheme 1). [26] …”

“…To this end, hydroxyl derivatives 25 – 27 were prepared from the corresponding keto compounds 10 – 12 and 23 by following a sequence involving the bridge‐head allylation and allyl Grignard addition reactions (Scheme 6). [26] …”