Organocatalytic [4+2] Benzannulation Between 1,4-Dithiane-Based Enal and Nitroolefins to Access 2-Nitrobiaryls

Indresh Kumar; Imtiyaz Ahmad Shah; Yadav Kacharu Nagare; Krishnan Rangan; Eldhose Iype; Ruchika Sharma; Rajni Kant

doi:10.1002/asia.202401408

Organocatalytic [4+2] Benzannulation Between 1,4-Dithiane-Based Enal and Nitroolefins to Access 2-Nitrobiaryls

Chem Asian J. 2025 Jan 14:e202401408. doi: 10.1002/asia.202401408. Online ahead of print.

Authors

Indresh Kumar¹, Imtiyaz Ahmad Shah², Yadav Kacharu Nagare², Krishnan Rangan³, Eldhose Iype⁴, Ruchika Sharma⁵, Rajni Kant⁵

Affiliations

¹ Birla Institute of Technology and Science - Pilani Campus: Birla Institute of Technology & Science Pilani, Chemistry, Vidya Vihar, Pilani, 333 031, Pilani, INDIA.
² Birla Institute of Technology and Science - Pilani Campus: Birla Institute of Technology & Science Pilani, Department of Chemistry, INDIA.
³ Birla Institute of Technology & Science Pilani - Hyderabad Campus, Department of Chemistry, INDIA.
⁴ American University of the Middle East, College of Engineering and Technology, KUWAIT.
⁵ Jammu University: University of Jammu, Post-Graduate Department of Physics & Electronics, INDIA.

PMID: 39807969
DOI: 10.1002/asia.202401408

Abstract

A simple method for constructing unsymmetrical 2-nitrobiaryls has been developed between substituted 1,4-dithiine-2-carbaldehyde and nitroolefins under metal-free conditions. To gain the advantage of the HOMO-raising effect of temporary substitutions on in situ generated dienamine intermediate, the present protocol established [4+2] benzannulation of 1,4-dithiane-tethered enals with nitroolefin. Further, easy unmasking of 1,4-dithiine units results in a benzannulation product like that of unsubstituted enals, which are difficult to access. Several 2-nitrobiaryls have been accessed with moderate to good yields and with promising synthetic applications.

Keywords: Organocatalysis; amine-catalysis; benzannulation; nitroolefins; theoretical calculations.