Synthesis and X-Ray Crystal Structure of Pyrrolo[1,2-a]benzimidazoles

 By

 Prof. Adel M. Awadallah

Islamic University of Gazae-mail: awada@iugaza.edu.ps

• Contents• * Introduction

• * Reaction of Nitrilimines with 2- Cyanomethylbenzimidazole

• * Reaction of Nitrilimines with 2- aminobenzimidazole

• * Reaction of Nitrilimines with 2- Aminopyrimidine

•Introduction• *Nitriles in 1,3-Dipolar Cycloaddition

– Synthesis of Heterocycles

• General Equation

YX z

N

R

N

YX z

R

+-

Examples

• Y. Al-Soud, N. Al-Masoudi, A. R. S. Ferwanah, Bioorganic & Medicinal Chemistry, 2003, 11, 1701 – 1708.

N

NO

CH3

CH3

CH3 Ph

N

N N

CH3

Et

N

NN

N

N N

CONH-N=CH

OH

H

H

OH

H

HO

HO

H

CH2OH

• Reaction of Nitrilimines with 2-Cyanomethylbenzimidazole

• (Expecting to get a triazole derivative)

NNO

CH3Cl

N

NH

N

N

NN

ClCH3

O

NHN

+-

C18H14ClN5O

M. Wt = 351

• ResultsM. Wt = 333 (351 – 18) → H2O is lost

IR (CN is present, but no C=O)

Suggested Structure

• Elwan, N. Tetrahedron, 2004, 60, 1161-1166.

Cl

NH

NCH3

O

Ar

N

NH

NC

NH

N

N N

CH3

Ar

N

NN

Ar

NH

N

N

CH3

+Et3N

1a,b

2

4a

3a (75%), 3b (65%)

a Ar = 4-ClC6H4

b Ar = 4-BrC6H4

Literature

Which is the correct structure????

  Mass SpectraIR Spectra1H-NMR 13C-NMR2D-NMR

  

Can not Help 

X-Ray 

Will Help 

X-Ray Crystal Structure of the Product

Another Example of Structure

Determination Problems 

N N

NNS

H

CH3

O

N N

NNO

CH3

CH2CH2OH

N N

NNO

CH3

CH2CH2OH

AcOH

-+

Lit 1

Lit 2

Which is the correct structure????

Mass SpectraIR Spectra1H-NMR 13C-NMR

 

Can not Help 

X-Ray 

Will Help

 

Lit 1: L. A. Vlasova, I. Ya. Postovskii, Khim. Geterotsikl. Soedin. 1971, 7, 700

Lit 2: A. Awadallah, P. Rademacher, R. Boese, J. Prakt. Chem. 1995, 337, 636 - 640

• Reaction of Nitrilimines with 2-aminobenzimidazole

 

Cl

NH

NCH3

O

Ar

N

NH

NH2

NH

NN

N N

CH3

Ar

N NHCH3

O

Cl

N

N

NH2

+Et3N

1a

5

7a

a Ar = 4-ClC6H4

6a (85%)

M. Wt 327 / 329

• Spectral Data• MS m/z (327/329 M+., chlorine isotopes).• IR (KBr) υ 3416,3310,3297(3NH), 1683(C=O) cm-1

• 1H-NMR (DMSO-D6) δ 2.5 (s, 3H, CH3), 6.4 (s,

2H, NH2), 6.6 (1H, d, 7.0 Hz, ArC-H), 6.8 (1H, t, 7.0

Hz, ArC-H), 7.0 (1H, t, 7.0 Hz, ArC-H), 7.2 (1H, d, 7.0 Hz, ArC-H), 7.4 (4H, 2d, 9.0 Hz, 4-ClC6H4), 11.0 (s,

1H, NH);• 13C-NMR (DMSO-D6) δ 191.2 (C=O), 155.1, 144.7

(2C=N), 142.6, 134.1, 128.8, 126.7 (4ArC), 129.6, 121.7, 118.9, 117.0, 115.4, 108.1 (6ArC-H), 25.6 (CH3)

• Reaction of Nitrilimines with 2-Aminopyrimidine

Cl

NH

NCH3

O

Ar

N

N

NH2

N

N

N

N N

CH3

Cl

N

NN

N

N

CH3

O

Cl

NN

N

CH3

O

Cl

N

N

+

Et3N

M. Wt 271 / 273

M. Wt 287 / 289

M. Wt 287 / 289

(11 different kinds of carbon)

(10 different kinds of carbon)

• Spectral Data•  MS m/z (287 / 289 M+., chlorine isotopes).• IR (KBr) υ No NH(s), No C=O• 1H-NMR (DMSO-D6) δ 2.51 (s, 3H, CH3),

5.51 (1H, t, 11.0 Hz, ArC-H), 7.55 (2H, d, 9.0 Hz, ArC-H), 7.65 (1H, d, 11.0 Hz, CH), 7.92 (2H, d, 9.0 Hz, ArC-H), 8.66 (1H, d, 11.0 Hz, C-H),

• 13C-NMR (DMSO-D6) δ 191.66 (C=O), 169.44, 160.96, 129.42, 124.99, 101.55 (5 Ar C-H), 161.44, 157.62, 136.82, 132.00 (4Ar C), 27.29 (CH3)

لحسن • لكم شكرااستماعكم

لجامعة • موصول والشكراألقصى

الله • ورحمة عليكم والسالم وبركاته