O-ARYLATION OF ANGULAR DIAZAPHENOXAZINE AND RELATED CARBOCYCLIC ANALOGUE USING BUCHWALD CATALYST

ABSTRACT

Synthesis   of twelve   O-arylated   diazabenzo[a]phenoxazine-5-one  and  its carbocyclic  analogue  is reported  in 46  –  99  % yields.    The  intermediates were  prepared  by  anhydrous  base  catalyzed  reaction  of 2,3-dichloro-1,4- naphthoquinone  with  4,5-diamino-6-hydroxyl-2-mercaptopyrimidine  and 2- aminophenol.   The  O-arylation   process   occurred   smoothly   in  non-polar solvent,   toluene    with   the   inexpensive    base,   KPO,   at    110C.    The intermediates  were combined with a variety of electron-deficient, electrically neutral and electron-rich phenols in the presence of a catalyst combination  of Pd(OAc)» and electron rich, bulky alkyldiary/phosphine ligand in which the alkyl groups  are tert-butyl  (t-Buxphos),  to furnish the arylated  compounds. Bulky yet basic  nature of the phosphine  ligand  is thought  to be responsible for these transformations. The highest yields were obtained when the intermediates   coupled   with   electron   rich  phenols,   with   the  carbocyclic analogue  giving  better  yields.   IR,   ‘H  NMR  and  ‘C NMR  spectra  data, confirmed the structures  of all the synthesized  compounds.  The effect  of the synthesized   compounds   on  bacteria   and  fungi  growth  was  studied.  The studied  compounds  were  found  to  be  potent  antibacterial   and  antifungal agents  as  they  showed  significant  biological  activity  against  Escherichia coli, Staphylococcus  aureus, Bacillus subtilis, Pseudomonas aeruginosa and Candida albicans.  In addition, they may be useful as dyes in industries since they absorb in the UV- visible region.

1.0     INTRODUCTION

CHAPTER ONE

1.1 BACKGROUND OF STUDY:

Angular phenoxazines  are defined as the polynuclear phenoxazines  that have non-linear  arrangement  ring  system’.  Angular phenoxazines  and its  aza analogues constitute important  classes of organic compounds because  of their wide range of commercial uses.  They are used as dyes 1     and drugs.  They exhibit

strong   biological    activities    rangmg    from    antidepressant,

ant1. tumour4,

anticancer,   antibacterial,   and  antituberculosis’  and  schizophrenia   agents’. Among the several industrial applications of angular phenoxazine derivatives are their   use   as   acid-base   indicator’,   biological   stains”,   laser   dyes”   and chromophoric compounds’.

The report of the basic structure of the parent phenoxazine I prompted the synthesis of several hundreds of derivatives, not only to improve their usefulness but also to open up new area of applications.

c£H ;

1

These structural modifications  have given rise to benzo[a]phenoxazine  2,

benzo[c]phenoxazines    3,   benzo[b]phenoxazine    4,   benzou]phenoxazine    5,

benzo[i]phenoxazine 6 and benzo[h]phenoxazine 7″ among others.  These are all

carbocyclic phenoxazines.

Structures  4  and 6  are  linear phenoxazines  while  structures  2,  3,  and 5  are angular phenoxazines.

Phenoxazine   compounds   that   have   two   benzo   groups   attached   to phenoxazine nucleus are called dibenzophenoxazines.  These include compounds8, 9, and 10.

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