Facile and efficient synthesis of homoallylic alcohols using allyl bromide and commercial zinc dust

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Facile and efficient synthesis of homoallylic alcohols using allyl bromide and commercial zinc dust
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  Pergamon 0040-4039(95)00877-2 Tetrahedron Letters, Vol. 36, No. 27, pp. 4885-4888, 1995 Elsevier Science Ltd Printed in Great Britain 0040-4039/95 9.50+0.00 Faclle and Efficient Synthesis of Homoallylic lcohols Uslno Ally Bromide and Commercial Zinc Dust Brindaban C. Ranu, Adinath Majee and Asish R. Das Department of Organic Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Calcutta - 700 32, India. bstract : An efficient procedure for the preparation of homoallylic alcohols has been achieved by a simple reaction of an aldehyde or a ketone with allyl bromide and commercial zinc dust in tetrahydrofuran. Synthesis of homoallylic alcohols by allylation of carbonyl compounds is one of the most important processes in organic synthesis 1 since the homoallylic alcohols can be easily converted to many important building blocks for natural product synthesis. 2 Acyclic stereocontroi during the carbon-carbon bond formation has also increased the importance of this process. 3 Different methods have been developed based on the use of a variety of metals such as magnesium, 4 zinc 5 and tin.6However, zinc offers certain specific advantages being moderately reactive to allow the preparation of polyfunctional allylzinc derivatives 7 and avoiding the formation of side products ,derived from the reductive coupling of the carbonyl compound such as the pinacol condensation, often observed using other reagents. 8 However, the preparation of 9 allylzinc derivatives is reported to require activated zinc to initiate the reactions. Sdveral methods have been reported to activate zinc such as washing with HCI solution, 10 ultrasound irradiation in the presence of lithium, 11 the use of Zn/Cu couple, 12 reduction of zinc chloride with alkali metals, 13 or electroreduction of zinc 9 chloride, among others. Considering the increasing importance of the allylzinc compounds in organic synthesis, 1 we sought to devise a simple and straighforward procedure for its preparation avoiding the additional step for preparation of activated zinc. Very interestingly, we have observed a clean and smooth reaction of allyl bromide with commercial zinc dust in tetrahydrofuran forming the allylzinc bromide which adds on to aldehyde or ketone to produce the corresponding homoallylic alcohol in excellent yield. To the best of our knowledge, we are not aware of any report of use of commercial zinc dust without being activated for an efficient allylation reaction. TM However, similar reactions in aqueous medium 15 or in presence of some additive 16 are known. O Zn OH Br THF ~ 4885  4886 Table 1. Allylatima of Carboeyl C~pound$ with Allyl Bromide and Zn-dust entry carbonyl compound time (h) product yleld(~) a 1 1.5 80 0 2 3 92 0 0 q ~ 0.5 0 s ph,,~ 1 O 5 ph ~ 2 O ? ph..~p h 2.s O 8 "~6 H 1.5 0 9 ph,.~H 3 0 o ~H 0 11 ph.~.~H 6 1.5 H O L.. ~ ph/~ ph/~ H O. /. ~ Ph/~Ph OH OH OH OH 9q 85 89 91 88 90 91 b 9q  4887 Table (contd .... ) entry cart)oayl compound time h) product yield ~)a 12 2 85 13 i, uj,~ 2 92 ill -~ ~ 3 90 CO 2 Et CO 2 Et o 15 c ~ 2 76 aAII yields refer to pure isolated products, bThis compound decomposes duri,g purification through column chromatography over silica gel. CThe reaction was carried out with crotyl bromide. The experimental procedure is very simple and straightforward. The allyl bromide 1 retool) in THF 1 mlJ was added dropwise to a stirred suspension of commercial zinc dus~ 1 mmol) in THF 2 ml) at room temperature and the mixture was stirred for half an hour after which the carbonyl compound I mmol) in THF 1 rnl) was added. Stirring was continued for a certain period of time as required to complete the reaction TLC). The reaction mixture was decomposed with a few drops of water and extracted with ether. The ethereal extract was washed with brine, dried over Na2SO and evaporated to leave the crude product which was purified by filtering it through a short column of silica gel. Several structurally different aldehydes and ketones underwent allylation by this procedure to produce the corresponding homoailylic alcohols in excellent yields. The results are summarized in Table 1. The reactions are reasonably fast and clean. The reaction condition is mild enough not to affec¢ the conjugated as well as the isolated double bond and carboxylic ester functionality entries ]0-14). This  4888 procedure is also regioselective as the reaction of crotyl bromide with ~:yclohexanone gives only (>95~, gc) the Y-addition product (entry 15). AIIyI Chloride is found to be much less reactive than allyl bromide as it has been observed that the reactions of allyl chloride with cyclohexanone and 1-octanal under identical conditions are only I0-15~ complete. 14 Zinc dust from different sources are found to give the same results. Following the same procedure, the propargy bromide also reacts with cyclohexanone and octanal to produce the correesponding acetylenic alcohols in very good yields. This demonstrates the further scope and potentiality of this simple procedure. To sum up, the present procedure for allylation of carbonyl compounds using commercial zinc dust provides much improvement over the existing methods and thus, will make a useful and important addition to the present methodologies. Further investigations to find the useful applications of this methodology are in progress and will be reported shortly. Acknowledgements : This investigation has enjoyed the support of CSIR, New Delhi through a grant to B.C.R. A.M. and A.R.D. are also thankful to CSIR for their fel Iowsh ips. References and Notes 1. (a) Jubert, C.; Nowotny, S.; Kornemann, D.; Antes, 1.; Tucker, C.E.; Knochel, P. J. Org. Chem. 1992, 57, 6384. (b) Wipf, P.; Lira, S. J. Chem. Soc. Chem. Common. 1993, 165q. (c) Yamamoto, Y.; Asao, N. Chm. Rev. 1993, 93, 2207. (d) Kobayashi, S.; Nishio, K. J. Org. Chem. 19911, 59, 6620. (e) Clayden, N.; Julia, M. J. Chem. Soc. Chem. Commun. 199q, 1905. 2. (a) Kim, E.; Gordon, D.M.; Schmid, W.; Whitesides, G.M.J. Org. Chem. 1993, 58, 5500. (b) Kadota, I.; Matsukawa, Y.; Yamamoto, Y. J. Chem, Soc. Chem. Common. 1993, 1638. 3. (a) Hoffman, R.W. Angew. Chem. Int. Ed. Engl. 1982, 21, 555. (b) ~'amamoto, ~'. Acc. Chem. Res. 1987, 20, 2q3. q. Blomberg, C.; Hartog, F.A. Synthesis 1977, 18. 5. Jubert, C.; Knochel, P. J. Org. Chem. 1992, 57, 5425. 6. Zhou, J.-Y.; Chen. Z.-C.; Wu, S.-H. J. Chem. Soc. Chem. Commun. 199Ji, 2703. 7. Lambert, F.; Kirschleger, B.; Villeras, J. J. Organomet. Chem. 1991, 405, 273. 8. Furstner, A.; Csuk, R.; Rohrer, C.; Weidmann, H. J. Chem. Soc. Perkin Trans. 1. 1988, 1729. 9. Roll in, Y.; Derien, S.; Dunach, E.; Gebehenne, C.; Perichon, J. Tetrahedron 1993, q9, 7723. 10. Hauser, C.R.; Breslow, O.S. Organic Synthesis, Wiley, N.Y., 1955, Collect Vol. III, p. 408. 11. Boudjouck, P.; Thompson, D.P.; Ohrbohm, W.H.; Han, B.H. Organometallics 1986, 5, 1257. 12. Santaniello, E.: Manzocchi, A. Synthesis 1977, 698. 13. Rieke, R.D.; Li P.T.J.; Burns, T.P.; Uhm, S.T.J. Org. Chem. 1981, q6, q323. lq. The reaction of crotyl chloride with cyclohexanone in presence of ordinary zinc produced the corresponding homoallylic alcohol in only 20~ yield as reported in ref. 9. 15. (a) Pettier, C.; Luche, J.-L. J. Org. Chem. 1985, 50, 910. (b) Sjoholm, R.; Rairama, R.; Ahonen, M. J. Chem. Soc. Chem. Commun. 19911, 1217. 16. (a) Gawronsky, J.K. Tetrahedron Lett. 198q, 25, 2605. (b) Picotin, G.; Miginiac, P. J. Org. Chem. 1987, 52, q796. Received in UK 29 March 1995; accepted 19 May 1995)
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