Facile Synthetic Route to [3.n]Thiacyclophanes through Ring‐Closing Metathesis and their Structural Studies

Abstract

We report a useful synthetic strategy to assemble constrained [3.n] thiacyclophanes using Grignard reaction and Ti(OiPr)4 assisted ring‐closing metathesis (RCM). This method is viable to access para, metapara, and meta isomers of thiacyclophanes. The structures of thiacyclophanes were confirmed unambiguously by single‐crystal X‐ray diffraction studies and compared with computationally optimized structures. It is implied that out of four methods (ab initio and DFT), MP2/6‐31G (d,p) is reasonably a better method for predicting structural parameters for this class of thiacyclophanes.

Modular Approach to Benzofurans, 2H‐Chromenes and Benzoxepines via Claisen Rearrangement and Ring‐Closing Metathesis: Access to Phenylpropanoids

“…Since, Ru catalyst 23 used for double bond isomerization is expensive, we explored an alternative method for this purpose and the double bond migration of 27 a-c was attempted with potassium tertbutoxide (KO t Bu) in THF to produce compound 28 a-c in 89-94% yields, but as a mixture of all four geometrical isomers, without any clear preference for either one of these. RCM [35] of 28 a-c catalyzed by second-generation Grubbs catalyst 22 [28b,c] (5 mol%) furnished benzofurans 29 a-c in 84-85% yield (Scheme 1).…”

“…Afterwards, compounds 30 a-c were treated under similar reaction conditions involving allyl bromide in the presence of potassium carbonate (K 2 CO 3 ) in acetone at reflux temperature to afford rearranged ally ether derivatives 31 a-c in good yields (95-96%). Finally, these precursors 31 a-c were subjected to RCM with the aid of catalyst 22 [35] (5 mol%) and a series of 2Hchromenes 32 a-c were produced in 90-92% yields. Finally, these 2H-chromenes 32 a-c were subjected to hydrogenation in the presence of Pd/C (10 mol%), under hydrogen (balloon) atmosphere at room temperature (rt) in ethyl acetate (EtOAc) for 4 h, to provide the 2H-chromanes 33 a-c in 93-94% yields (Scheme 2).…”

(E)-3-Thia-1,5(1,3)-dibenzenacycloundecaphan-8-ene-6,11-dione 3,3-dioxide

“…For the synthesis of the compound 1, we started with the preparation of the dialdehyde 2 (Kotha et al, 2020). Later on, a Grignard reaction with 2 gave 3, which on further oxidation provided the sulfone 4.…”

“…We have prepared novel thiacyclophanes using a simple strategy involving the Grignard reaction and ring-closing metathesis as key steps (Kotha et al, 2020). In this work, we present the single-crystal XRD study of the thiametacyclophane 1, which has two benzyl rings attached to an SO 2 moiety and a bridge at the meta positions of the phenyl rings containing two carbonyl functions connected by a double bond (Fig.…”

“…Their shapes are the main cause for their applications in supramolecular chemistry (Xu et al, 2008), material science (Yu et al, 2006) and medicinal chemistry (Lee et al, 2002). To this end, the synthesis of sulfur-containing cyclophanes (thiacyclophanes) has become of great interest for chemists (Nicolaou et al, 2010).We have prepared novel thiacyclophanes using a simple strategy involving the Grignard reaction and ring-closing metathesis as key steps (Kotha et al, 2020). In this work, we present the single-crystal XRD study of the thiametacyclophane 1, which has two benzyl rings attached to an SO 2 moiety and a bridge at the meta positions of the phenyl rings containing two carbonyl functions connected by a double bond (Fig.…”