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Synthesis of 1-Arylamino-5-alkoxycarbonyl-1H-tetrazolesLuca Bruché a , Luisa Garanti a & Gaetano Zecchi aa Dipartimento di Chimica Organica e Industrialedell'Università, Centro CNR per la Sintesi eStereochimica di Speciali Sistemi Organici, Via Golgi19, 20133, Milano, ItalyPublished online: 23 Sep 2006.

To cite this article: Luca Bruché , Luisa Garanti & Gaetano Zecchi (1992) Synthesisof 1-Arylamino-5-alkoxycarbonyl-1H-tetrazoles, Synthetic Communications: AnInternational Journal for Rapid Communication of Synthetic Organic Chemistry, 22:2,309-314

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SYNTHETIC COMMUNICATIONS, 2 2 ( 2 ) , 3 0 9 - 3 1 4 ( 1 9 9 2 )

SYNTHESIS OF l-ARYLAMINO-5-ALKOXYCARBONYL-1H-TETRAZOLES -

* Luca Bruch6, Luisa Garanti, Gaetano Zecchi

Dipartinento di Chimica Organica e Industriale dell 'Universit;,

Centro CNR per la Sintesi e Stereochimica di Speciali Sistemi

Organici, Via Golgi 19, 20133 Milano, Italy

Some l-arylamino-5-alkoxycarbonyl-1H-tetrazoles - (111) were

prepared, the key synthetic step being the 1,5-electrocyclic

closure o f - C-azidoinines (11) under thionyl chloride catalysis.

It is known that several tetrazole derivatives exhibit

biological activity and find application as pharmaceuticals and

agrochemicals.' Owing to our interest in this field, we aimed to

synthesise a series o f tetrazoles bearing a peculiar pattern of

substitution, i .e. 1 -aryl amino-5-a1 koxycarbonyl-1H-tetrazol es

(111). - -

* To whom correspondence should be addressed.

309

CoDvrkht @ 1992 bv Marcel Dekker. Inc.

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310 BRUCHE, G A R A N T I , AND ZECCHI

I n the l i g h t of t he known propensity of - C-azidoimines t o

afford t e t r azo le s - via 1 ,5-electrocycl ic c losure,* we devised the

synthet ic sequence i 1 l u s t r a t ed in the Scheme. The hydrazonyl

chlor ides ( I ) , prepared by a standard p r ~ c e d u r e , ~ were

e f f i c i en t ly converted i n t o the corresponding - C-azidohydrazones

(11) upon react ion with sodium azide under phase-transfer

conditions. Somehow unexpectedly, compounds ( I I were re luc tan t

t o undergo the 1 ,5-e lec t rocyc l ic c losure upon heat treatment;

under forced condi t ions, they suffered exclus vely degradative

processes. However, on considering t h a t t he polar i sa t ion of a 4 poliene system i s known t o f a c i l i t a t e i t s e lec t rocyc l ic c losure,

we decided t o inves t iga te the behavior of azides (11) under Lewis

acid c a t a l y s i s . Hence, compound ( I I a ) was t r ea t ed w i t h an

assortment o f potent ia l c a t a l y s t s ( s e e Table 1 ) ; the

corresponding t e t r azo le ( I I I a ) was r ea l ly formed in a y i e ld

markedly dependent on the promoting species . On the bas i s of

these r e s u l t s , compounds ( I Ib-g) were successful ly transformed

in to the desired t e t r a z o l e s ( I I Ib -g ) upon heating in the presence

of two equivalents of thionyl chlor ide ( see Table 2 ) .

Experimental

Melting points were determined on a Buchi apparatus and are

uncorrected. IR spec t ra were recorded with a Perkin-Elmer 298

spectrophotometer. Mass spec t ra were determined with a VG-70 EQ

apparatus. NMR spectra were recorded with a Varian EM-390 and a

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1-ARYLAMINO-5-ALKOXYCARBONYL-1H-TETRAZOLES - 311

Scheme

COOR' I

NH-N=C-N,

COOR' I

____) NH-N=C-CI R R

(a) : R = H, R ' = Me

(b) : R = 2-Me, R' = Me

(c) : R = 4-Me, R' = Me

(d) : R = 3,5-Me2, R' = Me

(e) : R = 4-N02, R' = Et

(9 : R = 2-COMe, R' = Et

(9) : R = 4-CI, 2-C0(4-CICeH4), R' = Et

COOR'

Table 1 . Ca ta lys t ' s Effect on the 1,5-Electrocyclisation of ( I I a )

mol. eq. time,

c a t a l y s t o f c a t a l y s t solvent temp. h y i e l d ,%

AlCl 2 CHCl room 3 20

BF3* E t 0 2 CHCl reflux 1 19

CH3COCl /py 2 Et20 room 70 11 2

SOC$ 1 CHCl re f lux 24 15

SOCl 2 CHC13 ref lux 18 48

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312 BRUCHE, G A R A N T I , AND ZECCHI

Table 2. Preparation and Characterisation o f Tetrazoles ( 1 1 1 )

- 1 reaction yield, rnp, 1R.m m l z entry time,h % " C a ( n u j o l ) 'H NMR (CDC13),d - _

18

4

24

12

21

8

20

48 60 3240 1740

10 b 3310 1750

31 90-91 3250 1740

65 119 3240 1740

71 148 3320

1750

32 152-153 3220 1740

1720

25 158 3300

1740

1650

3.88 (s,3H), 6.5-7.3 (rn,5H), 219

8.8 (br s,lHl 2.46 (s,3H), 3.97 (s,3H), 6.1- 233

6.3 (m,lH1, 6.8-7.3 (m,3H), 8.3 (br s,lH) 2.20 (s,3H), 3.88 (s,3H), 6.5- 233 7.0 (m,4H), 8.3 (br s,lH)

2.31 (s,6H), 4.07 (s,3H), 6.3- 247 7.3 (rn,3H), 8.2 (br s,lH) 1.48 (t,3H,J=7Hz), 4.58 (q,2H, 275

J=7Hz), 6.8-7.0 (rn,2H), 8.2-

8.4 Im,2H), 8.5 (br s,lH)

1.17 (t,3H,J=7Hz), 2.58 (s,3H), 278 4.25 (q,2H,J=7Hz), 5.9-6.1 (m,

lH), 6.7-7.3 (rn,2H), 7.7-7.9 (m,lH), 11.6 (br s, lH)

1.42 (t,3H,J=7Hz) , 4.45 (q,2H, 405 J=7Hz), 6.2-6.4 (m,lH), 7.2-

7.8 (rn,6H), 11.0 (br s, lH)

a From di i sopropyl ether. Undistillable oil.

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1-ARYLAMINO-5-ALKOXYCARBONYL-1H-TETRAZOLES - 313

Bruker WP8OSY instrument, using TMS as in te rna l standard. A l l new

compounds gave sa t i s f ac to ry elemental analyses. 5 Compounds ( I Ia -d , f ,g ) are known in the l i t e r a t u r e .

Preparation o f - C-Azidohydrazone ( I I e ) . A solut ion of compound

( I e ) (8 mnol) in benzene (60 ml) was t rea ted with a solut ion of

sodi um azi de (80 mmol ) and hexadecyl t r i butyl phosphoni urn bromide

(0.4 mmol) in water (60 ml) . The mixture was heated a t 35°C and

s t i r r e d vigorously in the dark

removed and the organic solut ion was washed w i t h water and dr ied

over sodium su l f a t e . After evaporation o f the solvent under

reduced pressure, diisopropyl e ther was added and the c r y s t a l l i n e

product ( I I e ) was col lected by f i l t r a t i o n . Yield 52%; mp

135-136°C (from diisopropyl e t h e r ) ; I R , cm ( n u j o l ) : 3260, 2160,

1700; ' H N M R (CDCl,),& 1.47 (t ,3H,J=7Hz), 4.45 (q,2H,J=7Hz),

7.1-7.3 ( m , 2 H ) , 8.1-8.3 ( m , Z H ) , 8 .5 ( b r s , lH) ; - - m/z 278.

f o r 7 h . The aqueous layer was

-1

Preparation of Tetrazoles ( I I I a - 9 ) . General Procedure. A

solut ion of azidohydrazone ( I I a -g ) (2.0 mmol) and thionyl

chlor ide ( 4 . 0 mmol) in chloroform ( 5 0 ml) was refluxed f o r t he

time given in Table 2 . The solvent was evaporated under reduced

pressure and the residue chromatographed on a s i l i c a gel column

w i t h benzene-ethyl ace ta te 9 : l as e luant , t o give t e t r azo le

( I I I a -9 ) . See Table 2 .

Acknowledgement

With the f inanc ia l support of Consiglio Nazionale d e l l e Ricerche

(Rome), Progetto Final izzato "Chimica Fine 11".

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314 BRUCHE, GARANTI, AND ZECCHL

References

1. Butler, R.N. In Comprehensive Heterocyclic Chemistry;

Katritzky, A.R.; Rees, C.W., Eds.; Pergamon Press: Oxford,

1984; Vol. 5, p 791.

2. Tisler, M. Synthesis 1973, 123.

3. Shawali, A.S.; Pa/rka/nyi, C. J.Heterocycl.Chem. 1980, - 17, 833.

4. Epiotis, N.D. Angew.Chem.,Int.Ed.Engl. 1974, 13, 751. 5. Bruche, L.; Garanti, L.; Zecchi, G. J.Heterocyc1.Cheo. 1989,

- 2 6 , 619. Bruche, L.; Garanti, L.; Zecchi, G. J.Chem.Res.,

( S ) 1991, 2, (M), - 171. -

(Accepted in The Netherlands 6 August, 1991)

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