1.6- Dioxaspiro- -nonane

Total syntheses of naturally occurring molecules possessing l,7-dioxaspiro[4,4] nonane skeletons 99EJ01757. 

Succinic anhydride is dimerised to 1,6-dioxaspiro [4.4] nonane-2,7-dione by heating with sodium hydroxide. Modification of an existing procedure by adding further sodium hydroxide after the initial reaction led to a severe exothermic reaction after heating for some 30 h which fused the glass flask to the heating mantle, probably at a temperature approaching 550°C. The reason for this was not known [1], At elevated temperatures and under influence of alkali, succinic acid condenses decarboxylatively beyond the dimeric spiroacetal, sometimes explosively. Contamination of the anhydride with base is to be avoided [2],... 

Figure 22. Interconversion profiles due to inversion of configuration (enantiomerization) of 1-chloro-2,2-dimethylaziridine and 1,6-dioxaspiro[4.4]nonane determined by complexation gas chromatography on nickcl(II) bis[3-(heptafluorobutnnoyl)-(1 / )-camphorate] 148,203 boxed profile calculated chromatogram202.

Reaction of 3-formyl-2-methoxy-l,6-dioxaspiro[4.4]nonanes (70) with 51 gave 71 (93IZV2004) (Scheme 16). 

Succinic anhydride is dimerised to 1,6-dioxaspiro [4.4] nonane-2,7-dione by heating with sodium hydroxide. Modification of an existing procedure by adding further... 

Photoirradiation of inclusion crystals of 3-oxo-2-cyclohexanecarboxamide derivatives (69b-69d) with the optically active host compound 12b as a water suspension for 4 hr gave optically almost pure 2-aza-l, 5-dioxaspiro[3,5]nonane derivatives (70b-70d) [38], Optically pure 70b and 70c were prepared by the... 

Optically active 19a was previously obtained by inclusion complexation with N -benzylcinchon idi um chloride 21 [36], Compound 21 was also a very efficient resolving agent for rac-17 [37], Crystal structure analysis of a (1 1) complex of 21 and selectively included (+)-17 showed that the molecular aggregate was associated by formation of a Cl HO hydrogen bond. Racemic compound 20 could be efficiently resolved only by complexation with (R,R)-(—)-trans-2,3-bis(hydroxydiphenylmethyl)-l,4-dioxaspiro[4.4]nonane 3b. A crude inclusion complex of 1 1 stoichiometry of 3b was formed selectively with (+)-20 in a 2 1 mixture of dibutyl ether/hexane. One recrystallization from the above combination of solvents gave a 34 % yield of the pure complex. Optically active (+)-20 was obtained by dissolving the complex in 10% NaOH, followed by acidification with HC1 and then recrystallization. The optical purity determined by HPLC (Chiralpack As) was >99.9 %. As far as we know, this is the only report of the resolution of 4,4 -dihydroxybiphenyl derivatives. Conversely, an inclusion... 

On close inspection of the chromatograms, an elevated baseline can be discerned between the terminal peaks of the spiroketals. This peak distortion is caused by interconversion of the stereoisomers during separation. On-column enantiomerization leads to the formation of a plateau between the terminal peaks (Trapp et al., 2001). Such a kinetic phenomenon of molecular interconversion was first observed for 1.6-dioxaspiro[4.4]nonane... 

Figure 11. Semi-preparative-scale stereoisomeric separation of 1.6-dioxaspiro[4.4]nonanes on Ni-CAR2 (experimental conditions cf. text) (Schurig, 1987).

Schurig, V. (1987) Semi-preparative enantiomer separation of l,6-dioxaspiro[4.4]nonanes by complexation gas chromatography, Naturwissenschaften 74, 190-191. 

Francke W., Heeman V., Gerken B., Renwick J. A. A. and Vite J. P. (1977) 2-Ethyl-l,6-dioxaspiro[4.4]nonane, principal aggregation pheromone of Pityogenes chalcographus (L.). Naturwissenschaften 64, 590. 

Adkins and co-workers found that hydrogenation of 3-(2-furyl)acrolein over nickel catalysts was accompanied by the formation of l,6-dioxaspiro[4.4]nonane (54) (eq. 12.108). The amount of the spiro compound 54 formed was greater over Ni-ki-... 

Scheme 12.28 The pathway leading to the formation of l,6-dioxaspiro[4,4]nonanes in hydrogenation of y-(2-I u ryI)al kanoI s.

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