Realizing 1,1-Dehydration of Secondary Alcohols to Carbenes: Pyrrolidin-2-ols as a Source of Cyclic (Alkyl)(Amino)Carbenes

Ayan Das; Benedict J Elvers; Mithilesh Kumar Nayak; Nicolas Chrysochos; Srinivas Anga; Amar Kumar; D Krishna Rao; Tharangattu N Narayanan; Carola Schulzke; Cem B Yildiz; Anukul Jana

doi:10.1002/anie.202202637

Realizing 1,1-Dehydration of Secondary Alcohols to Carbenes: Pyrrolidin-2-ols as a Source of Cyclic (Alkyl)(Amino)Carbenes

Angew Chem Int Ed Engl. 2022 Jul 11;61(28):e202202637. doi: 10.1002/anie.202202637. Epub 2022 May 6.

Affiliations

¹ Tata Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad 500046, Telangana, India.
² Institut für Biochemie, Universität Greifswald, Felix-Hausdorff-Straße 4, 17489, Greifswald, Germany.
³ Department of Aromatic and Medicinal Plants, Aksaray University, Aksaray, 68100, Turkey.

Abstract

Herein we report secondary pyrrolidin-2-ols as a source of cyclic (alkyl)(amino)carbenes (CAAC) for the synthesis of CAAC-Cu^I -complexes and cyclic thiones when reacted with Cu^I -salts and elemental sulfur, respectively, under reductive elimination of water from the carbon(IV)-center. This result demonstrates a convenient and facile access to CAAC-based Cu^I -salts, which are well known catalysts for different organic transformations. It further establishes secondary alcohols to be a viable source of carbenes-realizing after 185 years Dumas' dream who tried to prepare the parent carbene (CH₂ ) by 1,1-dehydration of methanol. Addressed is also the reactivity of water towards CAACs, which proceeds through an oxidative addition of the O-H bond to the carbon(II)-center. This emphasizes the ability of carbon-compounds to mimic the reactivity of transition-metal complexes: reversible oxidative addition and reductive elimination of the O-H bond to/from the C(II)/C(IV)-centre.

Keywords: 1,1-Dehydration; Carbenes; Dehydrogenation; Elimination; Hydrated Carbenes.