Recent Advances for the Construction of Seven-Membered Ring Catalyzed by N-Heterocyclic Carbenes

doi:10.6023/cjoc202109020

Abstract

The seven-membered rings represent an important structural motif and have found wide presence in natural products, biologically active molecules and drugs. In contrast to the five- and six-membered rings, the construction of seven- membered ring remains challenging. Thus, the developing efficient strategies for the synthesis of seven-membered rings is very desirable. N-Heterocyclic carbene (NHC) organocatalysis has been recognized as a powerful and unique tool for the quick construction of complex molecular architectures. Nevertheless, whereas significant advances have been made using NHC as catalysis. However, most of these works concentrated on the assembly of five or six-membered rings. This review highlights the developments and new advances for the construction of seven-membered rings catalyzed by NHC. The aim of this review is to provide an overview of this area and inspire synthetic chemists to develop more efficient and novel strategies for the construction of seven-membered rings.

Key words: N-heterocyclic carbenes, seven-membered ring, asymmetric synthesis, organocatalysis

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Ting Yao, Jiayan Li, Jiaming Wang, Changgui Zhao. Recent Advances for the Construction of Seven-Membered Ring Catalyzed by N-Heterocyclic Carbenes[J]. Chinese Journal of Organic Chemistry, 2022, 42(4): 925-944.

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Fig. & Tab. 42

Figure 1. Selected examples of natural products and drugs containing seven-membered ring

Scheme 1. Synthesis of 1,3-diazepine structure catalyzed by NHC

Figure 2. Mechanism for the synthesis of 1,3-diazepine

Scheme 2. Synthesis of 1,2-diazepine structure catalyzed by NHC

Figure 3. Mechanism for the synthesis of 1,2-diazepine

Scheme 3. Synthesis of 1,2-diazepine structure catalyzed by NHC

Figure 4. Mechanism for the synthesis of 1,2-diazepine

Scheme 4. Synthesis of benzoazepine structure catalyzed by NHC

Scheme 5. Synthesis of spirocyclic oxindole-benzofurazinone catalyzed by NHC

Figure 5. Mechanism for the synthesis of spiro-1,2-diazepine

Scheme 6. Synthesis of benzofurazepine catalyzed by NHC

Figure 6. Mechanism for the synthesis of benzofurazepine

Scheme 7. Synthesis of 1,5-benzodiazepine structure catalyzed by NHC

Figure 7. Mechanism for the synthesis of 1,5-benzodiazepine

Scheme 8. Synthesis of spiro-lactam hydroxyindole catalyzed by NHC

Figure 8. Mechanism for the synthesis of spiro-lactam hydroxyindole

Scheme 9. Synthesis of aza[1,2-α]-indole by cooperative NHC and benzenesulfinate

Figure 9. Mechanism for the synthesis of aza [1,2-α]-indole

Scheme 10. Synthesis of aza [1,2-α]-indole catalyzed by NHC

Figure 10. Mechanism for the synthesis of aza [1,2-α]-indole

Scheme 11. Synthesis of 4-azalactone catalyzed by NHC

Figure 11. Mechanism for the synthesis of 4-azalactone

Scheme 12. Synthesis of benzodioxepinone catalyzed by NHC

Figure 12. Mechanism for the synthesis of benzodioxepinone

Scheme 13. Synthesis of benzo-ε-lactone catalyzed by NHC

Figure 13. Mechanism for the synthesis of benzo-ε-lactone

Scheme 14. Synthesis of ε-lactone structure catalyzed by NHC

Figure 14. Mechanism for the synthesis of ε-lactone

Scheme 15. Synthesis of thiazole fused ε-lactone catalyzed by NHC

Figure 15. Mechanism for the synthesis of thiazole fused ε- lactone

Scheme 16. Synthesis of bridged caprolactone through cooperative catalysis of NHC and lewis acid Ti(OiPr)4

Figure 16. Mechanism for the synthesis of bridged caprolactone

Scheme 17. Synthesis of spiro-benzoxanone catalyzed by NHC

Figure 17. Mechanism for the synthesis of spiro-benzoxanone

Scheme 18. Synthesis of benzo[1,5]dithiepin-2-one catalyzed by NHC

Figure 18. Mechanism for the synthesis of benzo [1,5] dithiepin-2-one

Scheme 19. Synthesis of benzazepine catalyzed by cooperative NHC/palladium

Figure 19. Mechanism for the synthesis of benzazepine

Scheme 20. Synthesis of ε-caprolactone catalyzed by cooperative NHC/Pd

Figure 20. Mechanism for the synthesis of ε-caprolactone

Scheme 21. Synthesis of 2,3-benzodiazepines structure catalyzed by cooperative NHC/Pd

Figure 21. Mechanism for the synthesis of 2,3-benzodiazepines

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