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Structural resolution of the stereochemistry of a spirooxirane derived from an α‐arylidene heterocyclic carbonyl. The crystal and molecular structure of 2‐( p ‐chlorophenyl)‐5‐phenyl‐7‐methyl‐1‐oxa‐5,6‐diazaspiro[2.4]hept‐6‐en‐4‐one
Author(s) -
Baker Ronald J.,
Lankin David C.,
Umrigar Pesi P.,
Griffin Gary W.,
Ege Seyhan N.,
Ragone Katherine S.,
Trefonas Louis M.
Publication year - 1983
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.5570200314
Subject(s) - chemistry , ring (chemistry) , steric effects , monoclinic crystal system , group (periodic table) , carbonyl group , crystallography , crystal structure , molecular orbital , enone , stereochemistry , molecule , organic chemistry
The stereochemical assignment of molecular geometry for α‐arylidene carbonyl compounds and spirooxirane derived from them have continued to be a challenging problem for which the most satisfactory solution continues to be an x‐ray diffraction structure determination. In that regard, the title compound (a spirooxirane) has been found to crystallize in the monoclinic space group P2 1/c with cell dimensions of a = 5.989(1)Å, b = 27.625(4)Å, c = 9.374(2)Å, β = 99.06(1)°. The structure of the compound has been determined, with the refinement to R = 0.059. The previous, tentative assignment of structure has been confirmed substantiating our prediction that the oxidation of the enone system proceeds with rotation of the phenyl group on the β‐carbon away from the carbonyl group, minimizing adverse steric interactions and allowing orbitals of the carbonyl group to overlap with those of the carbanionic center during the closure of the oxirane ring. The agreement between predictions based on nmr data and the x‐ray diffraction determination will support a stronger reliance on the nmr data predictions in subsequent studies.