Abstract
Deprotonation of N,N -dibenzyl-N "-aryltriazenes, either in liquid phase or on solid support, by a strong base (n -BuLi or LDA) leads to fragmentation of the N-N single bond to give an imine and a diazenyl anion, which decomposes by loss of nitrogen to the parent aryl anion. The imine is deprotonated to give a 2-aza allyl anion, which is subsequently trapped by electrophiles. As an overall result, this fragmentation of the T1 triazene anchoring group represents a new traceless cleavage mode of this linker. The same mode of fragmentation was observed for the T2 linker leading to 2-aza allyl anions in liquid phase. The dibenzylamino moiety is apparently crucial since pyrrolidinodiazenylarenes can be metallated at the heterocycle without cleavage.
Key words
triazenes - diazenyl anions - azaallyl anions - umpolung - solid phase synthesis
References
1 Zollinger H.
Diazo Chemistry
Vol. 1:
VCH;
Weinheim:
1994.
2 Nicolaou KC.
Boddy CNC.
Natarajan S.
Yue TY.
Li H.
Bräse S.
Ramanjulu JM.
J. Am. Chem. Soc.
1997,
119:
3421
3a Nelson JC.
Young JK.
Moore JS.
J. Org. Chem.
1996,
61:
8160
3b Bräse S.
Köbberling J.
Enders D.
Wang M.
Lazny R.
Brandtner S.
Tetrahedron Lett.
1999,
40:
2105
4 Kosower EM.
Acc. Chem. Res.
1971,
4:
193
5 Bräse S.
Enders D.
Köbberling J.
Avemaria F.
Angew. Chem. Int. Ed.
1998,
37:
3413
6 Gross ML.
Blank DH.
Welch WM.
J. Org. Chem.
1993,
58:
2104
7 Since the diethyl derivative is cleavable also (see below), the stability of the piperazine triazenes might be due to kinetic reasons.
H -pyrrole:
8a Scully FE.
J. Org. Chem.
1980,
45:
1515
8b Nakamura M.
Hirai A.
Nakamura E.
J. Am. Chem. Soc.
1996,
118:
8489
9 This reaction is similar to the aza-1,2-Wittig rearrangement reaction with concurrent loss of nitrogen.
10 Nutt RF.
Joullié MM.
J. Am. Chem. Soc.
1982,
104:
5852
11 Rademacher P.
Heymanns P.
Münzenberg R.
Woell H.
Kowski K.
Poppek R.
Chem. Ber.
1994,
127:
2073
12 Bozec-Ogor S.
Salou-Guiziou V.
Yaouanc JJ.
Handel H.
Tetrahedron Lett.
1995,
36:
6063
13a Seebach D.
Dach R.
Enders D.
Ranger B.
Jansen M.
Brachtel G.
Helv. Chim. Acta
1978,
61:
1622
13b Shibata N.
Katoh T.
Terashima S.
Tetrahedron Lett.
1997,
38:
619
13c Schmitz E.
Sonnenschein H.
Gründemann C.
J. Prakt. Chem.
1980,
322:
261
14a Seebach D.
Angew. Chem. Int. Ed. Engl.
1979,
18:
239
14b The ‘Umpolung’ was referenced to the change of a a2 -synthon to a d2 -synthon similar to the use of N -nitrosoamines.
15a Kauffmann T.
Ahlers H.
Echsler K.
Schulz H.
Tilhard H.
Chem. Ber.
1985,
118:
4496
15b Quang L.
Gaessler H.
Quang Y.
Angew. Chem. Int. Ed. Engl.
1981,
20:
922
15c Pearson WH.
Lian BW.
Angew. Chem. Int. Ed.
1998,
37:
1724
16 van Maanen H.
Kleijn H.
Jastrzebski JBTH.
van Koten G.
Bull. Soc. Chim. Fr.
1995,
132:
86
17 Bower DJ.
Howden MEH.
J. Chem. Soc., Perkin Trans. 1,
1980,
672
18a Klötgen S.
Fröhlich R.
Würthwein E.
Tetrahedron
1996,
52:
14801
18b Klötgen S.
Würthwein E.
Tetrahedron Lett.
1995,
36:
7065
19 Millington CR.
Quarrell R.
Lowe G.
Tetrahedron Lett.
1998,
39:
7201
20 Stieber F.
Grether U.
Waldmann H.
Angew. Chem. Int. Ed.
1999,
38:
1073
21 Kirchhoff JH.
Bräse S.
Enders D.
J. Comb. Chem.
2000,
3:
71
22 Bräse, S. unpublished results.
23 Nishiwaki K.
Ogawa T.
Matsuo K.
Angew. Chem. Int. Ed.
2002,
41:
484
24 All new non-polymeric compounds were characterized by means of NMR, MS, IR, and elemental analysis.
