Lactonization of camphene-8-carboxylic acid

Abstract

1062 (s), 998, 973 (s), 956 (s), and 902 (s) cm-1; nmr (CHCla) 6 3.9 (br s, 2 H), 3.5 (br unresolved m, 2 H), 2.0 (m, 5 H), and 1.61 (br s, 7 H). A sample of 10 was prepared according to the directions of Appleton, et aZ.,* and spectral comparison showed it to be idenlical with the 5% diol above.The 2% component (11) was not isolated in pure form, being contaminated with stopcock grease and traces of alumina. This crude material (84 mg) was stirred at 25' with 75 ml of 0.0125 M potassium periodate solution and 7.5 ml of 2.0 N sulfuric acid for 24 hr. Titration according to the directions given by Jacksonz4 showed that periodate equivalent to 17.4 mg of diol was consumed.The 46% component (9) was isolated as a crystalline solid and was purified by sublimation: mp 118-121"; ir (KBr) 3320, 1150 (w), 1074, 1052 (s), 1034, 1008 (s), 996, 906, and 720 cm-l; ir (CClr) 2930, 2872, 2856, 1468, and 1466 cm-'; nmr (CHCla) 6 4.05 (br s, 2 H), 3.49 (m, 2 H), 2.16 (m), 1.93 (br s), 1.58 (br s), and 1.0-2.4 (12 H). A sample (118 mg, 0.76 mmol) of this diol was oxidized with periodate as described above. In 24 hr a t 26", ll3Y0 of the theoretical amount of periodate was consumed. The reaction mixture was concentrated in vacuo, saturated with sodium chloride, and extracted with chloroform. The extracts were dried (MgSOI) and the solvent was evaporated to give 130 mg of solid, mp 154-156', which reacted with dinitrophenylhydrazine and showed bands in the infrared at 2710 and 2810 cm-1. Treatment of the crude material with 30% hydrogen peroxide gave a crystalline acid, mp 153-155' (lit.16 mp 150-152').Enol Fraction.-Glpc examination of the enol fraction showed three components. The major component (23% of the solvolysis product or 50y0 of the enol fraction) was shown by glpc compari-(24) E. L. Jackson, Ow. Reactions, 2, 341 (1944). son (12 ft x 0.125 in. 5% FFAP column at 145') to be identical with the main component of the trifluoroacetolysis, L e . , 3 + 4.The minor component (3% of the solvolysis product or 6% of the enol fraction) was not isolated, but was shown by glpc comparison to be different from the hydride reduction products of either 5 or 6.A sample of the enol fraction (110 mg) was hydrogenated over palladium on charcoal in methanol solution. The main product was collected from a preparative gas chromatographic run: mp 176-178'; ir 3400, 2980, 1480, 1040, 982, 963, and 910 cm-1. The spectral data and melting point identify this as 2.Partial separation of the two main enol components was achieved in a preparative scale gas chromatography run on 5 ft X 0.25 in. 20% SE-30 on Chromosorb W column at 90". A crude sample enriched in component 7 (21% of the solvolysis mixture) was obtained: mp 127-131'; ir (CC11) 3620, 3360 (br), (m), and 985 cm-l (s); nmr (CClr) 6 5.5-6.0 (m, 2 H), 3.82 (unresolved, 1 H), 2.23 (m), 2.08 (s, 1 H), 2.0 (m), 1.5 (br s), and 1.2-2.4 (11 H). Compound 7 is reported" to melt a t 103-103.5', but the overlap between the peaks for enols 3 + 4 and 7, even on an analytical level, prevented isolation of p...

Solvolytic Studies on Methylnorbornyl Systems: Investigations on the Synthesis of 2-Exo-methyl-6-norbomylideneacetic Acid

“…A 3,2-methyl shift is not anticipated due to its exo-selectivity. 2,6-Hydride shifts analogous to the proposed methyl shift have been observed in closely similar compounds [15,16].…”

The synthesis of norbornanes with functionalized carbon substituents at a bridgehead. 1-(3-Oxonorborn-1-yl)ethanone and 1-(3-oxonorborn-1-yl)-2-propanone

“…The combined extracts were dried and the solvent was removed to give a viscous, colorless oil, which was sublimed to give a mixture of the known (14,15) For personal use only.…”

Rearrangements in the acid-catalyzed formation of lactones from 2-hydroxynorbornane-2-acetic acid derivatives and related compounds

“…A column of silica gel that was packed in and eluted with dichloromethane was used in separating lactones 4, 5, and 6 from each other, lactone 4 being eluted first, followed by 5, and finally 6. Treatnzerzt of 2-hydroqnorborrzane-2-acetic acid (7). (E)-arzd (Z)-(norborn-2-ylidene (8 and 9), and the ethyl esters of the latter ( I 0 and I I ) with concentrated sulfuric ctcid.…”

“…The same consideration can be invoked as a supplementary or alternative explanation of the failure to observe the formation of 23 from 12. A further point of interest arises from this report (7). It concerns the origin of 22, for which the authors propose ring closure of 27, which arises from 25 by a Wagner-Meerwein shift to 28, followed by an endo-6,2-hydride shift to 29 and another Wagner-Meerwein rearrangement to 27.…”