Abstract:Most conformational molecular switches based on amide skeleton had been limited in their use in a solution. We developed a molecular switch with an amide skeleton, which is applicable without...
“…Upon analysis, we observed that 7 exhibited a predominant cis conformation (CD 2 Cl 2 at 216 K, 98%), as expected from the effect of the bulky N -substituents. , The cis conformation was also confirmed in the crystal structure (Figure and SI Section 1). Comparison of the conformational preferences of 5a and 7 suggests that hydrogenation and dehydration can serve as a molecular switch, analogous to the amide-based molecular switch demonstrated in our previous work. − …”
Methyl substitution at the double bond of N-alkenyl anilides influences both the preferred conformation and the susceptibility to acidic hydrolysis. The R 1 -substituted amide favors the trans conformation, whereas amides substituted at R 2 or R 3 favor the cis conformation. Substitution at the R 1 and R 3 positions increases the ratio of the trans conformer. DFT study indicated that these conformational preferences can be explained in terms of substituent-induced torsion twisting of the N-alkenyl moiety relative to the amide plane. R 1 substitution enhances the susceptibility to acidic hydrolysis, whereas R 2 or R 3 substitution increases the stability. The effect of the double bond on the conformational effect was showcased by contrasting the preferred conformation of R 1 -substituted anilide (trans) and hydrogenated N-isopropyl amide (cis).
“…Upon analysis, we observed that 7 exhibited a predominant cis conformation (CD 2 Cl 2 at 216 K, 98%), as expected from the effect of the bulky N -substituents. , The cis conformation was also confirmed in the crystal structure (Figure and SI Section 1). Comparison of the conformational preferences of 5a and 7 suggests that hydrogenation and dehydration can serve as a molecular switch, analogous to the amide-based molecular switch demonstrated in our previous work. − …”
Methyl substitution at the double bond of N-alkenyl anilides influences both the preferred conformation and the susceptibility to acidic hydrolysis. The R 1 -substituted amide favors the trans conformation, whereas amides substituted at R 2 or R 3 favor the cis conformation. Substitution at the R 1 and R 3 positions increases the ratio of the trans conformer. DFT study indicated that these conformational preferences can be explained in terms of substituent-induced torsion twisting of the N-alkenyl moiety relative to the amide plane. R 1 substitution enhances the susceptibility to acidic hydrolysis, whereas R 2 or R 3 substitution increases the stability. The effect of the double bond on the conformational effect was showcased by contrasting the preferred conformation of R 1 -substituted anilide (trans) and hydrogenated N-isopropyl amide (cis).
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