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Synthesis, crystal structure determination, and spectroscopic analyses of 1‐chloro‐2‐(2,6‐diisopropylphenyl)‐4,4‐dimethyl‐2‐azaspiro[5.5]undecane‐3,5‐dione: an unyielding precursor to a cyclic (alkyl)(amido)carbene
Author(s) -
Hudnall Todd W.,
Reinheimer Eric W.,
Dorsey Christopher L.
Publication year - 2021
Publication title -
acta crystallographica section c
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.304
H-Index - 17
ISSN - 2053-2296
DOI - 10.1107/s2053229621006173
Subject(s) - carbene , undecane , chemistry , crystal structure , deprotonation , steric effects , alkyl , crystallography , adduct , reactivity (psychology) , molecule , medicinal chemistry , stereochemistry , catalysis , ion , organic chemistry , medicine , alternative medicine , pathology
The synthesis, single‐crystal X‐ray structure, and 1 H and 13 C NMR spectrocopic analyses of an unyielding precursor molecule to a cyclic (alkyl)(amido)carbene, 1‐chloro‐2‐(2,6‐diisopropylphenyl)‐4,4‐dimethyl‐2‐azaspiro[5.5]undecane‐3,5‐dione, C 24 H 34 ClNO 2 ( 1 ), is reported. Despite the use of several bases, 1 could not be deprotonated to afford the corresponding carbene. The crystal structure of 1 was compared to the crystal structures of two structurally similar HCl adducts of stable carbenes (compounds 4 and 5 ), which revealed no significant differences in the geometries about the `carbene' C atoms. To better understand the reactivity differences observed for 1 when compared to 4 and 5 , modified percent buried volume (% V bur ) calculations were performed. These calculations revealed that the H atom bound to the carbene C atom is the most sterically hindered in compound 1 when compared to 4 and 5 (% V bur = 84.9, 81.3, and 79.3% for 1 , 4 , and 5 , respectively). Finally, close inspection of the quadrant‐specific % V bur values indicated that the approach of a deprotonating base to the H atom bound to the carbene C atom is significantly blocked in 1 (69.9%) when compared to 4 and 5 (50.4 and 56.5%, respectively).