¹³C NMR chemical shift assignments for some 2‐substituted cyclic 1,3‐diketones

Abstract

Complete 13C NMR chemical shift assignments are reported for 32 cyclic and one acyclic 1,3‐diketones, either unsubstituted or having one or two substituents at the 2‐position. The first two classes exist exclusively in the enol form in (CD3)2SO and as mixed tautomers in CDCl3.

Reactions of 1,2-Bis(trimethylsilyloxy)cycloalkenes with the Diethyl Acetals of Aldehydes

“…This was consistent with Mariano's observations . The sparing solubility of these 1,3-diketones in common solvents made their purification by flash chromatography problematic, and this lack of solubility necessitated the NMR analyses of the diketones in TFA solution, in which they were rapidly equilibrating enol forms …”

“…The yields of 1,3-diketones from the gem-dimethyl cyclobutene 12 with ketones and their acetals had been observed to be significantly lower than that with 1 due to competition with alternative rearrangement pathways. , In the present case with aldehyde acetals, the cyclobutanones ( 13 or 14 ) were produced easily, but their treatment with Amberlyst 15 resin in TFA did not yield 1,3-diketones, of which some would have been known compounds. , Instead, the products were enols of 1,2-diketones 15 (Scheme 3). These products could be rationalized by rearrangement of cyclobutanones 13 (i.e., migration of the bond to the dimethylcarbon competed favorably with migration of the bond to the carbonyl).…”

1,3,5‐Triamino‐1,3,5‐trideoxy‐cis‐inositol, a New Ligand with a Remarkable Versatility for Metal Ions. Part 2. Safe and efficient ligand preparation and structure of the free ligand and the CoIII complex

“…Rh(4%) + Pt(2%) on C, Pt(4%) + Rh(1 %) on C, the two diastereoisomeric ct,P-unsaturated cyclohexanones 6a and 6b have been detected as major by-products. The observed C,, symmetry of 6a and 6b in the NMR spectra (D,O) is a consequence of a fast equilibrium between two tautomeric forms for both compounds [13]. The formation of unsaturated cyclohexanones obviously indicate a premature stagnancy of H, uptake.…”