Chemistry

G. P. KUGATOVA, G. A. LAUMYANSKAS, G. K. KRASILNIKOVA,
V. V. MOZOLIS, and V. I. KALVELITE

SYNTHESIS AND TRANSFORMATIONS OF MONOCYCLIC SECONDARY ACETYLENIC ALCOHOLS

(Presented by Academician M. I. Kabachnik, February 29, 1960)

The subject of the present investigation is secondary acetylenic alcohols of types I–VII, synthesized from acetylene and $\Delta^{3}$-cyclohexene aldehydes VIII–XV, which are readily obtained by condensation of available dienes and dienophiles. We use such alcohols for constructing cycloaliphatic polyene systems closely related in their structure to natural ones. This can be accomplished either by hydration of the acetylenic bond in the alcohols under study, with conversion into ketols and then into tertiary acetylenic glycols, or by isomerization of secondary acetylenic alcohols into $\alpha,\beta$-unsaturated aldehydes and ketones, followed by extension of the side polyene chain:

\[ \begin{aligned} &\text{(cyclohexenyl)}{-}\mathrm{CH{=}CH{-}CHO} \;\leftarrow\; \text{(cyclohexenyl)}{-}\mathrm{CHOH{-}C{\equiv}CH} \;\xrightarrow{\mathrm{H_2O}}\; \\ &\longrightarrow\; \text{(cyclohexenyl)}{-}\mathrm{CHOH{-}C(=O){-}CH_3} \;\xrightarrow{\mathrm{CH{\equiv}CH}}\; \text{(cyclohexenyl)}{-}\mathrm{CHOH{-}C(OH)(CH_3){-}C{\equiv}CH}. \end{aligned} \]

The scant information on secondary acetylenic alcohols $({}^{1-6})$ and the absence of any data on the properties of acetylenic alcohols of the series selected by us made necessary a detailed and systematic study of their reactivity. The availability to us of such alcohols with different numbers, characters, and positions of substituents in the $\Delta^{3}$-cyclohexene ring made it possible to trace the influence of structural factors on the properties of the alcohols themselves, as well as of intermediate compounds obtained at later stages in the construction of complex cyclopolyene systems.

We synthesized the alcohols I–VII under study from acetylene and the corresponding $\Delta^{3}$-cyclohexene aldehydes VIII–XIV in the presence of sodium in liquid ammonia at temperatures from $-40$ to $-70^\circ$.* The starting aldehydes VIII–XV were obtained by diene condensation of acrolein, crotonaldehyde, and cinnamaldehyde with butadiene, piperylene, 2-methylbutadiene, or 1-phenylbutadiene; the condensation was carried out at $160$–$200^\circ$ in the presence of hydroquinone in a metal ampoule. The yields of monocyclic secondary acetylenic alcohols are 30–60% and depend to a large extent on the structure of the aldehyde taken. Thus, the para-substituted $\Delta^{3}$-cyclohexenal XII readily reacts with acetylene, whereas the ortho-substituted cyclohexenals IX, X, XI enter into this reaction with difficulty, and the phenyl-substituted aldehyde XV, under comparable conditions, does not react with acetylene at all. However, the influence of the character and position of the substituents is not observed for the hydrogenated analogs of the $\Delta^{3}$-cyclohexane aldehydes,—all of them ob-

* The reaction must be carried out in dimethoxymethane (and not in ether), using an excess of liquid ammonia, which makes it possible to considerably reduce the formation of a nitrogen-containing by-product.

form secondary acetylenic alcohols with great ease and in good yield.

\[ \begin{gathered} \text{VIII--XV} + HC{\equiv}CH \longrightarrow \text{I--VII} \\ \text{I--VII} \xrightarrow[\mathrm{HgSO_4,\ H_2SO_4}]{+H_2O} \text{XXX--XXXVI} \\ \text{I--VII} \xrightarrow[\mathrm{Pd/CaCO_3}]{H_2} \text{XVI--XXII} \\ \text{I--VII} \xrightarrow[\mathrm{Pd/CaCO_3\ or\ PtO_2}]{+3H_2} \text{XXIII--XXIX} \\ \text{XVI--XXII} \xrightarrow[\mathrm{Pd/SrCO_3\ and\ PtO_2}]{+2H_2} \text{XXIII--XXIX} \\ \text{XXIII--XXIX} \xrightarrow{\mathrm{KHSO_4}} \text{XXXVII--XLII} \\ \text{I--VII} \xrightarrow{+\mathrm{POCl_3}} \text{XLVII, XLVIII} \\ \text{XLVII, XLVIII} \xrightarrow[\mathrm{Pd/CaCO_3}]{H_2} \text{XLIX, L} \\ \text{XVI--XXII} \xrightarrow{+\mathrm{POCl_3}} \text{XLIX, L} \\ \text{XVI--XXII} \xrightarrow{\mathrm{KHSO_4}} \text{XLIII--XLVI} \end{gathered} \]

\[ \begin{aligned} &\text{I, VIII, XVI, XXIII, XXX, XXXVII, XLIII, XLVII, XLIX: } R_1=R_2=R_3=H \\ &\text{II, IX, XVII, XXIV, XXXI, XXXVIII, XLIV: } R_1=CH_3;\ R_2=R_3=H \\ &\text{III, X, XVIII, XXV, XXXII, XXXIX: } R_1=C_6H_5;\ R_2=R_3=H \\ &\text{IV, XI, XIX, XXVI, XXXIII, XL: } R_1=R_3=CH_3;\ R_2=H \\ &\text{V, XII, XX, XXXVII, XXXIV, XLI, XLV: } R_1=R_3=H;\ R_2=CH_3 \\ &\text{VI, XIII, XXI, XXVIII, XXXV: } R_1=H;\ R_2=R_3=CH_3 \\ &\text{VII, XIV, XXII, XXIX, XXXVI, XLII, XLVI, XLVIII, L: } R_1=R_2=H;\ R_3=CH_3 \\ &\text{XV: } R_1=CH_3;\ R_2=H;\ R_3=C_6H_5 \end{aligned} \]

Acetylenic alcohols I—VII are selectively hydrogenated over the Lindlar catalyst, or with 1 mole of hydrogen over a palladium catalyst, to the corresponding ethylenic alcohols XVI—XXII. Exhaustive hydrogenation of the acetylenic I—VII and ethylenic XVI—XXII alcohols is readily accomplished on Pd/CaCO₃ or PtO₂ and leads to their saturated analogs XXIII—XXIX.

Secondary acetylenic alcohols I—VII are hydrated in the presence of mercuric sulfate and sulfuric acid to the corresponding oxy ketones XXX—XXXVI. It should be noted here that hydration of acetylenic alcohols II and III does not proceed, and the alcohols are recovered unchanged; however, repeating the experiment with the alcohols recovered from the reaction leads to the corresponding ketols XXXI and XXXII.

Saturated alcohols XXIII, XXIV, XXV, XXVI, XXVII, XXIX are dehydrated rather easily and in quantitative yield to ethylenic hydrocarbons XXXVII—XLII on heating with potassium bisulfate at 160—190°. Dehydration of secondary ethylenic alcohols under the same conditions takes a different course—the alcohols XVI, XVII, XX, XXII form simple ethers XLIII—XLVI in good yield. Secondary acetylenic alcohols I—VII do not change under the indicated dehydration conditions with potassium bisulfate. If, however, their dehydration is carried out in the presence of phosphorus oxychloride, in pyridine under a nitrogen atmosphere, the corresponding hydrocarbons are obtained. Of the latter, hydrocarbons XLVII and XLVIII were isolated in analytically pure form; according to IR-spectral data, they are vinylacetylenic hydrocarbons with conjugated multiple bonds.* Dehydration of secondary ethylenic alcohols XVI

* The frequency of the acetylenic bond (2137 cm⁻¹) is more intense and is shifted downward by approximately 20 cm⁻¹ in comparison with that of the initial alcohol, and in the region of absorption frequencies of double bonds there are two frequencies: 1654 cm⁻¹, characteristic of the double bond in the ring, and 1635 cm⁻¹, more intense than the first. From the shift of the frequency characteristic of an acetylenic bond, and from the intensity of the 1635 cm⁻¹ frequency, one may infer conjugation of the acetylenic and ethylenic bonds in the molecules of hydrocarbons XLVII and XLVIII.

and XXII under the action of phosphorus oxychloride leads to the formation of hydrocarbons XLIX and L with conjugated ethylenic bonds; in the IR spectrum of these hydrocarbons there is an intense band (1602 cm\(^{-1}\)), which indicates conjugation of the multiple bonds in the molecule. The diethylenic hydrocarbons XLIX and L were obtained as a result of the selective hydrogenation of hydrocarbons XLVII and XLVIII. It should be noted that, in a number of cases, isolation of the products from the reaction mixture after dehydration with POCl\(_3\) is greatly hindered owing to resinification and the presence of chlorine-containing products. Therefore, from the ethylenic alcohols XVII—XXI and the acetylenic alcohols II—VI it was not possible to obtain analytically pure dehydration products (dehydration of such alcohols in the vapor phase with P\(_2\)O\(_5\) or with Al\(_2\)(SO\(_4\))\(_3\) led to resinification).

Table 1

The characteristics of the synthesized compounds are given in Table 1. All the saturated, ethylenic, and acetylenic alcohols obtained were additionally characterized in the form of acetates.

Institute of Chemistry and Chemical Technology
Academy of Sciences, Lithuanian SSR

Received
26 II 1960

CITED LITERATURE

1. A. I. Favorskaya, E. M. Auvinen, Yu. P. Artsybasheva, ZhOKh, 28, 1758 (1958).
2. I. N. Nazarov, G. A. Shvekhgeimer, Izv. AN SSSR, OKhN, 1956, No. 2, 199.
3. I. N. Nazarov, S. G. Matsoyan, ZhOKh, 27, 2115 (1957).
4. M. Julia, J. Surzur, Bull. Soc. chim. France, 1956, No. 5, 1615.
5. E. T. Clapreton, W. S. Gregor, J. Am. Chem. Soc., 72, 2501 (1950).
6. W. Reppe, Ann., 596, 1 (1955).