Syntheses of 2-ethyl-8-methyl-1,7-dioxaspiro[5.5]undecanols

Abstract

Synthetic approaches to ring-and side-chain hydroxy derivatives of the 2-ethyl-8-methyl-1,7-dioxaspiro-[ S Slundecane system 8 are described. Alkylation reactions of diethyl3-oxopentanedioate, pentane-2,4-dione and acetone N,N-dimethylhydrazone have been employed. Appropriate choices of enantiomeric iodides in the alkylation sequences, sometimes followed by asymmetric dihydroxylation of derived hydroxyenones, have permitted access to key enantiomers of these alcohols, which have been fully characterised by 'H and 3C NMR spectroscopy, gas chromatographic-mass spectrometric methods, and chiral gas chromatography.In previous publications 1-3 we have described the synthesis of a range of spiroacetals, many of which were components of insect secretions and emissions, particularly from Australasian fruit-16 17 902

13C NMR Analysis as a Useful Tool for Structural Assignment of Vinyl- and Dienyltin Derivatives

“…Replacement of a vinylic hydrogen by a tributylstannyl group in 1-tributylstannyl-1-propen-3 ol (1a, (E), 10,11 [comparison with prop-2-en-1-ol (1)] results in the a-car- In the following 2 (Z), 11 2 (E), 11 butenol and 3 (Z), 12 and 3 (E) 13 pentenol series, similar chemical shift variations can be measured for the a-and b-sp 2 -carbons and for the b'-and g-sp 3 -carbons ( Figure 4). In these examples, a deshielding of the geminal b'-sp 3 -carbons between +8.0 ppm and +5.0 ppm, and the g-sp 3 -carbons in a range of +0.5 ppm to +3.0 ppm, was also observed.…”

“…The values of 3 J 13 1,2-Distannyl derivatives such as 46 (Z) and 46 (E) were first prepared in a stereospecific way by Piers et al (Figure 22). 34 13 C NMR analysis of both isomers show no significant difference for 3 J 13 C-119,117 Sn coupling constant between the two E and Z isomers.…”

“…For the 117 and 119 isotopes, 1 H-119,117 Sn, 13 C-119,117 Sn, and 119 Sn-119 Sn spin-spin coupling constants can be observed and measured. 2 119 Sn NMR is a powerful analytical tool, 3 giving tin atoms chemical shifts, which are typical of the nature of the tin atom substitution.…”

“…The 3 J H-=-Sn which appears to be the most interesting argument for stereochemical assignment, by Leusink 6 clearly shows that 3 However, the measurement of 3 J H-=-Sn coupling constants becomes difficult due to multiplicity of the signals and/or overlap between stannyl satellites and other sig- In the literature, 13 C NMR studies of organotin compounds essentially deal with structural investigation of alkyltin derivatives using chemical shifts and coupling constant correlations, 8 very few 13 C NMR data have been reported for vinyl-or dienyltin derivatives. In 13 C NMR two different splitting figures are observed in the protondecoupled spectra.…”

“…The most important result gathered from 13 C NMR analysis arises from the 3 J Cg-=-Sn coupling constants. Preliminary work is due to Mitchell,9 In a preceding 13 C NMR study of tin compounds, we extended the results of Mitchell to a large number of vinyltin derivatives.…”