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Synlett 2004(7): 1203-1206  
DOI: 10.1055/s-2004-825597
LETTER
© Georg Thieme Verlag Stuttgart · New York

Highly Selective Isomerization of Allyloxyalcohols to Cyclic Acetals or 1-Propenyloxyalcohols

Magdalena Urbalaa, Nikodem Kuźnik*b, Stanisław Krompiecb, Józef Rzepac
a Szczecin University of Technology, Institute of Organic Chemical Technology, Puaskiego 10, 70-322 Szczecin, Poland
b Silesian University of Technology, Faculty of Chemistry, M. Strzody 7, 44-100 Gliwice, Poland
Fax: +48(32)2371205; e-Mail: nikodem@zeus.polsl.gliwice.pl;
c Silesian University, Institute of Chemistry, Szkolna 9, 40-006 Katowice, Poland
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Publication History

Received 14 January 2004
Publication Date:
10 May 2004 (online)

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Abstract

Highly selective isomerization of allyloxyalcohols either to 1-propenyl derivatives or to cyclic acetals of propanal depending on the transition metal (Ru, Rh) complex used is described together with a proposed explanation of an alternative reaction, which permits broad application of the described method.

Key words

isomerizations - cyclization - ruthenium complexes - ­acetals - vinyl ethers

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Standard Procedure of Isomerization: Allyloxyalcohol (scale 2-5 g), solvent (if applicable) and the catalyst (amount given in Table [1] ) were put into a glass screw-capped ampoule, purged with argon (for ca. 1 min), tightly capped and heated in an oil bath for given period of time (Table [1] ). Afterwards, solvent (if applicable) was evaporated using a rotary evaporator. The products were separated by distillation (760-0.1 mmHg; 1b, 2b, 1c-4c, 9b, 10b) or column chromatography (silica gel, 200-400 mesh, benzene-hexane 1:5; 3b-6b, 5c, 6c). (E)- and (Z)-4-(1-Propenyloxy)-1-pentanols ( 4b): 1H NMR (CDCl3): δ = 6.20 (d, 1 H, J = 12.5 Hz, CH3CH=CH-), 5.93 (dt, 1 H, J = 6.2 Hz, CH3CH=CH-), 4.75 (dt, 1 H, J = 12.6 Hz, CH3CH=CH-), 4.36 (dt, 1 H, J = 6.8, CH3CH=CH-), 3.59-3.73 [m, 5 H, -OCH 2 (CH2)3CH 2OH], 1.40-1.67 [m, 9 H, CH 3CH=, -(CH2)3-]. 13C NMR (CDCl3): δ = 145.6, 146.5 (Z,E-CH3CH=CH-), 98.5, 100.9 (Z,E-CH3 CH=CH), 69.0, 71.9 (=CHOCH2-), 62.2 (-CH2OH), 32.2 (-CH2CH2OH), 29.1, 29.6 (-OCH2 CH2-), 22.2 (-CH2-), 9.2, 12.6 (Z,E-CH3CH=). MS: m/e (rel. int.) = 144 (10) [M+], 87 (42), 69 (100), 58 (49), 57 (29), 41 (50), 43 (7). 2-Ethyl-1,3-dioxocane ( 4c): 1H NMR (CDCl3): δ = 4.38 (t, 1 H, -CH-), 3.38-3.64 (m, 4 H, -OCH2-), 1.53-1.67 [m, 6 H, -(CH2)3-], 1.40-1.47 (m, 2 H, CH3CH 2-), 0.91 (t, 3 H, CH3-). 13C NMR (CDCl3): δ = 104.3 (-CH-), 65.4 (-OCH2-), 29.7
(-CH2CH2 CH2-), 26.5 (-CH2 CH2CH2-), 23.0 (CH3 CH2-), 9.1 (CH3-). MS: m/e (rel. int.) = 144 (1) [M+], 115 (67), 85 (70), 69 (100), 67 (13), 57 (18), 56 (9), 41 (28), 43 (6).

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{[RuCl2 (COD)]x} (10 mg, 0.04 mmol) and tri(2,4,6-trimethoxyphenylphosphine) (19 mg, 0.04 mmol) were heated at 100 °C in THF (2 mL) for 3 h, then 2-allyloxy-ethanol 1a (0.77 g, 7.6 mmol) was added and heated at 80 °C for 3 h. Then, solvent was removed and the crude turned out to get the mixture of cyclic product 1c and (E)-2-(1-pro-penyloxy)ether 1b - NMR analysis.

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Benzyl-butyl Acetal of Propanal ( 9b): Allyl butyl ether 9a (3.92 g, 34.3 mmol), benzyl alcohol 11 (3.7 g, 34.3 mmol) and dichlorotris(triphenylphosphine)ruthenium(II) (65.8 mg, 0.069 mmol) were placed into a screw-capped ampoule. The mixture was purged with argon flow for 1 min. Then, after capping, the ampoule was placed into a thermostated oil bath at 120 °C for 3 h. After the reaction the product was vacuum distilled, yield 82%, bp 98 °C (5 mmHg). 1H NMR (CDCl3): δ = 7.38-7.22 (m, 5 H, Ph), 4.58 (dd, 2 H, J = 36.0, 11.8 Hz, PhCH 2O-), 4.53 [t, 1 H, J = 5.8 Hz,
-OCH(CH2CH3)O-], 3.53 (dt, 2 H, J = 9.4, 6.5 Hz,
-OCH 2CH2CH2CH3), 1.70 (qd, 2 H, J = 7.4, 5.8 Hz,
-CH 2CH3), 1.63-1.52 (m, 2 H, -OCH2CH 2CH2CH3), 1.47-1.34 (m, 2 H, -OCH2CH2CH 2CH3), 0.94 (t, 3 H, J = 7.4 Hz, -CH2CH 3), 0.93 (t, 3 H, J = 7.3 Hz, -OCH2CH2CH2CH 3). 13C NMR (CDCl3): d = 138.6 (Ph-C1), 128.4 (Ph-C2 and Ph-C6), 127.7 (Ph-C3,Ph-C5), 127.5 (Ph-C4), 103.8
[-OCH(CH2CH3)O-], 67.1 (PhCH2O-), 65.2
(-OCH2CH2CH2CH3), 32.0 (-OCH2 CH2CH2CH3), 26.4
(-CH2CH3), 19.5 (-OCH2CH2 CH2CH3), 13.9
(-OCH2CH2CH2 CH3), 9.1 (-CH2 CH3). MS: m/e (rel. int.) = 221 (5) [M+], 193 (24), 148 (18), 108 (20), 92 (20), 91 (100), 79 (20), 57 (23).