using water as solvent in the organic reactions is one of the most important targets to organic chemists because of the easy availability , nontoxicity , and ecofriendly nature of the water [ 17 ] . in this endeavour
, a number of chemical reactions such as diels alder , hetero diels - alder , 1,3-dipolar cycloaddition , oxidations , reductions , and others are performed successfully in water [ 13 ] .
also , it is reported that in few cases addition of the water increases the rate and the yield of a reaction and also enhances the enantioselectivity in a chiral synthesis .
but the main problems associated with water as a solvent is its poor ability to solubilise organic reactants and incapability to create anhydrous condition for moisture sensitive organic compounds and catalysts . to overcome the solubility problem , generally a surfactant is introduced to the reaction mixture .
the surfactant , due to its hydrophobic and hydrophilic nature , forms micelles with water insoluble organic compounds and promote the desired reactions to occur inside the hydrophobic ambience of the micelle core [ 9 , 10 ] .
cleavage of the c = n bonds is a very important transformation in organic synthesis as the c = n functionality is widely used to protect both the carbonyl and amines .
there are a number of methods used for the cleavage of c = n bonds which include acidic reagents [ 1113 ] , oxidizing agents , metallic salts [ 15 , 16 ] , ( phseo)2o , nahso3 , and others .
most of these methodologies suffer from serious drawbacks like involvement of strong lewis and bronsted acids , use of toxic and costly transition metals ( i.e. , cr , pd , co ) , low temperature , longer reaction time , low yield , and difficulties in isolating the products
. therefore , development of efficient , mild and environment friendly reagents are always necessary . on the other hand
, bisindoles are recently emerging as extremely important class of compounds because of their novel antibacterial and anticancer activities [ 1921 ] .
that is why a number of methodologies have also been postulated for the synthesis of bisindoles [ 2229 ] . in our previous communications
, we reported that surfactant- ( sds- ) mediated cleavage of c = n bonds could be achieved with acetic anhydride   and surfactant - i2-water can be used for the deprotection of imines to carbonyls .
we have also shown that bis- and tris ( indolyl)alkanes can be synthesized in presence of bronsted acid in water . in continuation of our research in hydrated media , herein , we wish to disclose the dual catalytic activity of the system i2-sds - h2o which behaves as a lewis acid   for the cleavage of 2,3-diaza-1,3-butadiene , 1-aza-1,3-butadienes , and oximes to produce carbonyls and amines , and the resulting reaction mixture reacts with indoles to produce bis ( indolyl)alkanes in situ at room temperature under neutral conditions .
for an initial study , molecular iodine was added to a mixture of 1,4-diphenyl-2,3-diaza-1,3-butadiene ( 1a ) ( 1  mmol ) and indole ( 2a ) ( 2  mmol ) in water .
it was presumed that the activated imine should produce carbonyl compound in the reaction mixture which might be trapped with indole .
but only a trace amount of 3,3-bis(indolyl)phenylmethane ( 3a ) was found to be formed in the reaction .
we envisioned that the poor yield of the product may be due to the insolubility of organic substrates in water .
accordingly , we added a surfactant ( sds ) to the reaction flask . to our delight ,
the reaction produced isolable amount of 3a as a brown solid but half of the 1,4-diphenyl-2,3-diaza-1,3-butadiene ( 1a ) left unreacted in the reaction mixture .
so amount of indole ( 2a ) was doubled ( 4  mmol ) and the same reaction condition successfully produced quantitative amount of 3a .
the product was filtered out and the filtrate was treated with freshly distilled benzaldehyde ( 0.05  mmol ) in ethanol which furnished 1a ( m.p .
this infers the simultaneous involvement of two c = n bonds of bis - anils , leaving behind hydrazine in the reaction mixture .
also , no self - reaction of individual starting materials leading to indole dimer   ( 4 ) or pyrrole formation   ( 5 ) were observed under the same reaction conditions ( scheme 1 ) .
optimization of the reaction conditions was undertaken by employing different catalyst loadings under various surfactant conditions .
it was found that the best result was obtained by the application of 15  mol% of i2 containing sodium dodecyl sulphate ( sds ) and water at room temperature ( entry 1 , table 1 ) . in absence of the catalyst no formation of 3a
was observed even after stirring for 24 hours ( entry 5 , table 1 ) . to study the scope and limitations of the reaction ,
i2-sds - h2o system was applied to the reaction of indole ( 2 ) and 2,3-diaza-1,3-butadiene derivatives ( table 2 , entries a 
the bisindoles were formed in excellent yields under the reaction condition . it was observed that the reaction was relatively faster when an electron withdrawing substituent , for example , no2 , was present in the phenyl ring of the 2,3-diaza-1,3-butadienes ( table 2 , entry e ) in comparison to the electron donating groups , for example , ome and oh ( table 2 , entries b and f ) .
identical results were obtained when 2-methylindole ( 2a ) was used in place of indole ( 2 ) ( table 2 , entries g and h ) .
all the products were characterized by their ir , h nmr , c nmr , and mass spectral data and also by comparison with the literature report ( scheme 2 ) [ 24 , 25 ] . in order to further explore the efficiency of the i2-sds - h2o system the reaction of the oximes 6 and indoles 2 was studied . when oximes ( 1  mmol ) and indole ( 2  mmol ) were allowed to react under the same reaction condition described earlier , bis - indolylalkanes formed ( table 3 ) . the product was filtered off and the filtrate was treated with benzaldehyde in ethanol .
the resulted product was benzaldoxime , which proved the liberation of hydroxylamine during the reaction .
it was found that no michael addition product   was formed and only a trace amount of indole dimer 5   could be identified .
the system was also applied to the reaction of 1-aza-1,3-butadienes 7 with indole ( 2 ) which produced bis ( indolyl)alkanes 8 in very good yield eliminating aryl amine in the reaction mixture ( table 4 ) .
all the products were well characterized by comparison of their spectral and mass data with that of the reported value [ 24 , 25 ] .
in conclusion , we have shown the dual catalytic activity of i2-sds - h2o system which deprotects the azadienes , oximes , and azabutadienes and produces bis ( alkyl)indoles in situ when indole is present in the reaction medium .
the two - step reaction can be carried out without using acid , transition metals , and organic solvents . besides , the reaction condition is mild and can be done in water under neutral condition which contributes to the criteria of green chemistry .
h nmr spectra were recorded on avance dpx 300  mhz ft - nmr spectrometer .
chemical shifts are expressed in  units relative to tetramethylsilane ( tms ) signal as internal reference .
ir spectra were recorded on ft - ir - system-2000 perkin elmer spectrometer on kbr pellets or in chcl3 .
the solvents for chromatography were distilled before use . in a 50  ml round bottom flask
, 15  mol% of i2 was first dissolved in water ( 10  ml ) .
2,3-diaza-1,3-butadiene ( 1  mmol ) and indole ( 4  mmol ) were added and stirred in the presence of sodium dodecyl sulphate ( sds ) ( 0.02  g ) for the stipulated time .
the product formed was filtered off and washed with water , dried , and recrystallized from ethanol .  
identical reaction condition was followed when 1-aza-1,3-butadienes and oximes were used as reactants . in this case , 2  mmol of indoles were used to react with 1  mmol of imines .
colorless solid ; mp : 150152c ; ftir ( kbr ) :  3418 , 3058 , 1623 , 1611 , 1445 , 1093  cm ; h nmr ( 300  mhz , cdcl3 ) :  5.95 ( s , 1h , ar 
ch ) , 6.73(s , 2h ) , 7.06 ( t , 2h , j = 6.8  hz ) , 7.187.27 ( m , 3h ) , 7.317.36 ( m , 2h ) , 7.367.42 ( m , 6h ) , 7.98 ( br , s , 2h , nh ) ; c nmr ( 75  mhz , cdcl3 ) : 40.7 , 111.2 , 119.1 , 119.5 , 120.4 , 122.1 , 123.8 , 126.9 , 126.9 , 128.2 , 129.1 , 136.8 , 144.8 ; hrms calcd for c23h18n2 ( m ) : 322.2851 , found 322.2832 ; anal.calcd . : c , 85.70 ; h , 5.59 ; n , 8.69 ; found c , 85.75 ; h , 5.56 ; n , 8.56 .  
pink solid ; mp : 76 - 77c ; ftir ( kbr ) :  3415 , 3060 , 1491 , 1465 , 1095  cm ; h nmr ( 300  mhz , cdcl3 ) :  5.91 ( s , 1h , ar  ch ) , 6.76 ( s , 2h ) , 7.08 ( t , 2h , j = 8.3  hz ) , 7.22 ( t , 2h , j = 7.9  hz ) , 7.287.42 ( m , 8h ) , 8.01 ( br , s , 2h , nh ) ; c nmr ( 75  mhz , cdcl3 ) : 39.8 , 111.5 , 122.6 , 123.8 , 127.1,128.4 , 129.8 , 130.1 , 130.9 , 131.0 , 131.6 , 137.2 , 143.5 ; hrms calcd for c23h17n2cl ( m ) : 356.7371 ; found 356.7324 ; anal.calcd .
: c , 77.52 ; h , 4.77 ; n , 7.86 ; found c , 77.48 ; h , 4.72 ; n , 7.80 .  
brown solid ; mp : 323325c ; ftir ( kbr ) :  3420 , 1720 , 1455 , 1258  cm ; h nmr ( 300  mhz , cdcl3 ) :  5.98 ( s , 1h , ar - ch ) , 6.85 ( s , 2h ) , 7.107.55 ( m , 11h ) , 8.05 ( br , s , 2h , nh ) ,
c nmr ( 75  mhz , cdcl3 ) : 34.8 , 107.0 , 110.0 , 111.5 , 117.8 , 119.9 , 120.0 , 122.5 , 124.8 , 127.1 , 136.8 , 142.2 ; hrms calcd for c21h16n2o2 ( m ) : 312.2621 ; found 312.2611 ; anal.calcd .
c , 80.84 ; h , 5.12 ; n , 8.97 ; found c , 84.05 ; h , 5.15 ; n , 8.94 .
the spectral data of the compounds are available in the supplementary material available online at doi : 105402/2012/635835 .
 a novel catalytic system consisting of i2-sds - h2o has been developed which cleaves 2,3-diaza-1,3-butadiene , 1-aza-1,3-butadienes , oximes and in presence of indoles in the medium uses the corresponding aldehyde products to produce bis(indolyl)alkanes in situ . 
 this one pot simple and mild dual catalytic system works in water at room temperature under neutral conditions . 
1. Introduction
2. Results and Discussion
3. Conclusions
4. Experimental