Abstract
The scope and limitation of lithium-ethylenediamine-THF-mediated reductive bond cleavage at the α-position of aromatics were examined. Very mild conditions such as lithium metal (5 equiv) and ethylenediamine (7 equiv) in oxygen-free THF were quite effective for the demethylation of aromatic ethers even at as low as -10 °C. Allyl benzyl ethers were also deprotected under these conditions with very little change of the allylic alcohol moiety. Through this study, 2,6-dimethylbenzyl (m -xylylmethyl, MXM) group was developed as an alternative of benzyl group, which is readily cleavable under the above mentioned reductive conditions.
Key words
electron transfer - ethers - lithium - phenols - protective groups
References
1 Birch AJ.
Quart. Rev.
1950,
69
2 Kaiser EM.
Synthesis
1972,
391
3a Sartoretto PA.
Sowa FJ.
J. Am. Chem. Soc.
1937,
59:
603
3b Kranzfelder AL.
Verbanc JJ.
Sowa FJ.
J. Am. Chem. Soc.
1937,
59:
1488
3c Weber FC.
Sowa FJ.
J. Am. Chem. Soc.
1938,
60:
94
4 Birch AJ.
J. Chem. Soc.
1947,
102
5 Reggel L.
Friedel RA.
Wender I.
J. Org. Chem.
1957,
22:
891
6 Mejer S.
Gawecka K.
Jablonski L.
Roczn. Chem.
1977,
51:
2477
7 Jablonski L.
Kotlarek W.
Mejer S.
Bull. Acad. Polon. Sci. Ser. Sci. Chim.
1975,
24:
101
8 Garst ME.
Dolby LJ.
Esfandiari S.
Fedoruk NA.
Chamberlain NC.
Avey AA.
J. Org. Chem.
2000,
65:
7098
9 Mann FG.
Pragnell MJ.
J. Chem. Soc.
1965,
4120
10 Node M.
Ohta K.
Kajimoto T.
Nishide K.
Fujita E.
Fuji K.
Chem. Pharm. Bull.
1983,
31:
4178
11 Nishioka H.
Nagasawa M.
Yoshida K.
Synthesis
2000,
243
12 Chakraborti AK.
Sharma L.
Nayak MK.
J. Org. Chem.
2002,
67:
6406
13 Hurd CD.
Oliver GL.
J. Am. Chem. Soc.
1959,
81:
2795
14 Eagle DH.
J. Org. Chem.
1963,
28:
1703
15 Zimmerman HE.
Wang PA.
J. Am. Chem. Soc.
1993,
115:
2205
16 Yus M.
Foubelo F.
Ferrández JV.
Chem. Lett.
2002,
726
17 Hwu JR.
Wein YS.
Leu Y.-J.
J. Org. Chem.
1996,
61:
1493
18 Hwu JR.
Chus V.
Schroeder JE.
Barrans RE.
Khoudary KP.
Wang N.
Wetzel JM.
J. Org. Chem.
1986,
51:
4731
19 Groth U.
Schölkopf U.
Tiller T.
Tetrahedron
1991,
47:
2835
20 Liu H.-J.
Yip J.
Shia K.-S.
Tetrahedron Lett.
1997,
38:
2253
21 Alonso E.
Ramón DJ.
Yus M.
Tetrahedron
1997,
53:
14355
22 Shi L.
Xia WJ.
Zhang FM.
Tu YQ.
Synlett
2002,
1505
23 Makabe H.
Kong LK.
Hirota M.
Org. Lett.
2003,
5:
27
24 2,6-Dimethylbenzyl group is possible to be abbreviated as DMB, The DMB group, however, is already well know as 2,4-dimethoxybenzyl group. We propose here the MXM group (m -xylylmethyl) to avoid the confusion in future.
25 Brown CA.
Yamashita A.
J. Am. Chem. Soc.
1975,
97:
891
26 Doolittle RE.
Org. Prop. Proc. Int.
1981,
13:
179
27 Davis R.
Muchowski JM.
Synthesis
1982,
987
28 Soloshonok VA.
Tang X.
Hruby VJ.
Tetrahedron
2001,
56:
6375
29 Cardani C.
Casnati G.
Piazzi F.
Cavalleri B.
Gazz. Chim. Ital.
1958,
88:
487
30 Rang S.
Strenze T.
Muurisepp M.
Eisen O.
Org. Mass Spectrom.
1984,
19:
193
31 Tateiwa J.
Hayama E.
Nishimura T.
Uemura S.
J. Chem. Soc., Perkin Trans. 1
1997,
1923
32 Dupont G.
Dulou R.
Pigerol C.
Bull. Chim. Soc. Fr.
1955,
638
33 Ali SS.
Echner H.
Kahn KM.
Schroder C.
Hasan M.
Rahaman A.-U.
Voelter W.
Z. Naturforsch. B: Chem. Sci.
1994,
49:
1425
34 Deck LM.
Brazwell EM.
Vander Jagt DL.
Royer RE.
Org. Prep. Proced. Int.
1990,
22:
495
35 Konig WA.
Faasch H.
Heitsch H.
Colberg C.
Hausen BM.
Z. Naturforsch., B: Chem. Sci.
1993,
48:
387
36 Tsatsas G.
Guioka-Dedopoulou V.
Bull. Soc. Chim. Fr.
1964,
10:
2610
37 Gonzalez AG.
Barrera JB.
Rodriguez Perez EM.
Z. Naturforsch., C: Biosci.
1991,
46:
12
38 Schmalz H.-G.
Volk T.
Bernicke D.
Huneck S.
Tetrahedron
1997,
53:
9219
39 Miyakoshi T.
Togashi H.
Synthesis
1990,
407
40 Bates RB.
Siahaan TJ.
J. Org. Chem.
1986,
51:
1432
41 Baudin J.-B.
Itka B.-W.
Hareau G.
Julia SA.
Lorne R.
Pascard C.
Tetrahedron
1991,
47:
6655
42a Jankowski P.
Marczak S.
Masnyk M.
Wicha J.
J. Organomet. Chem.
1991,
403:
49
42b Zhang Z.-B.
Wang Z.-M.
Wang Y.-X.
Liu H.-Q.
Lei G.-X.
Shi M.
J. Chem. Soc., Perkin Trans. 1
2000,
53
43 Cook BR.
Reinert TJ.
Suslick KS.
J. Am. Chem. Soc.
1986,
108:
7281
