Premium
Abnormal N‐Heterocyclic‐Carbene‐Mediated Fixation of CO 2 and N 2 O, and the Activation of Tetrahydrofuran and Tetrahydrothiophene under Ambient Conditions
Author(s) -
Thakur Arunabha,
Vardhanapu Pavan K.,
Vijaykumar Gonela,
Kumar Hota Pradip,
Mandal Swadhin K.
Publication year - 2016
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201501303
Subject(s) - chemistry , tetrahydrothiophene , adduct , carbene , lewis acids and bases , tetrahydrofuran , furan , nuclear magnetic resonance spectroscopy , medicinal chemistry , molecule , crystal structure , reagent , crystallography , stereochemistry , catalysis , organic chemistry , solvent
A strong σ‐donor abnormal N‐heterocyclic carbene ( a NHC), 1,3‐bis(2,6‐diisopropylphenyl)‐2,4‐diphenylimidazol‐5‐ylidene ( L1 ), reacted with B(C 6 F 5 ) 3 in the presence of CO 2 and N 2 O to form the adducts [ a NHC · CO 2 · B(C 6 F 5 ) 3 ] ( 1 ) and [ a NHC · N 2 O · B(C 6 F 5 ) 3 ] ( 2 ), respectively, in high yields at room temperature within a very short period of time. Furthermore, this a NHC/B(C 6 F 5 ) 3 reagent system was found to be very efficient for the ring‐opening of tetrahydrofuran (thf) and tetrahydrothiophene (tht), affording 3 and 4 , respectively, within 5–10 min at room temperature in good yields. Interestingly, this a NHC forms the air‐stable Lewis acid/base adduct [ a NHC · B(C 6 F 5 ) 3 ] ( 5 ) with B(C 6 F 5 ) 3 in the absence of any suitable substrate upon keeping this mixture in solution. DFT calculations showed that the Lewis acid/base adduct 5 is energetically less stable than compounds 1 – 4 , and this may be the driving force for the formation of compounds 1 – 4 in the presence of small molecules such as CO 2 , N 2 O, thf and tht. All the new compounds were characterized spectroscopically ( 1 H, 13 C, 19 F and 11 B NMR, IR spectroscopy) in solution and the solid‐state structures were unambiguously established by single‐crystal X‐ray diffraction analysis.