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Struktur des Zwischenproduktes einer (i‐PrO) 2 TiMe 2 ‐Methylierung: NMR‐Untersuchungen und Konformationsanalyse
Author(s) -
Hollenstein Sandro,
Hesse Manfred
Publication year - 1996
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19960790325
Subject(s) - chemistry , ring (chemistry) , lactone , stereochemistry , crystallography , nmr spectra database , heteronuclear single quantum coherence spectroscopy , atom (system on chip) , proton nmr , selectivity , nuclear magnetic resonance spectroscopy , medicinal chemistry , spectral line , catalysis , organic chemistry , physics , astronomy , computer science , embedded system
Structure of the Intermediate of a Methylation with (i‐PrO) 2 TiMe 2 : NMR Investigations and Conformational Analysis The intermediate of the reaction of 3‐(1‐nitro‐2‐oxocyclohexyl)propanal ((±)‐ 1 ) with (i‐PrO) 2 TiMe 2 was shown to be a titanium salt of 6‐(hydroxynitroryl)decano‐9‐lactone. 1 H‐, 13 C‐, HSQC‐, 1 H, 1 H‐TOCSY‐ and long‐range HMBC‐NMR spectra of this intermediate indicate a complexation of the carbonyl O‐atom and an O‐atom of the hydroxynitroryl group to the same Ti‐atom. The product of the reaction ( t ‐3‐methyl‐ c ‐6‐nitro‐2‐oxabicyclo[4.4.0]decan‐ r ‐1‐ol, (±)‐ 2 ) was reacted with several titanium reagents to give also titanium salts of the 6‐(hydroxynitroryl)decano‐9‐lactone. Monte Carlo studies and MM3 * force‐field calculations of the anion of 6‐(hydroxynitroryl)decano‐9‐lactone, 3′ , resulted in a conformation of the ten‐membered ring (only 9.57 kJ/mol higher in energy than the global minimum), which allows the Ti‐atom to coordinate to the O‐atom of the N(O)OH and CO group at the same time. With the suggested structure of 3′ · TiR n , we are able to explain the selectivity of the reaction.