Selective Hydrogenation of Nitriles to Secondary Imines Catalyzed by

Apr 25, 2017 - (18) These reactions proceed at high temperature and pressure (140 °C, 60 bar H2) and high catalyst loadings (5 mol %), resulting in a...
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Letter

Selective Hydrogenation of Nitriles to Secondary Imines Catalyzed by an Iron Pincer Complex Subrata Chakraborty, and David Milstein ACS Catal., Just Accepted Manuscript • Publication Date (Web): 25 Apr 2017 Downloaded from http://pubs.acs.org on April 25, 2017

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ACS Catalysis

Selective Hydrogenation of Nitriles to Secondary Imines Catalyzed by an Iron Pincer Complex Subrata  Chakraborty  and  David  Milstein*   Department  of  Organic  Chemistry,  Weizmann  Institute  of  Science,  Rehovot,  76100,  Israel ABSTRACT:   Selective   hydrogenation   of   nitriles   to   secondary   imines   catalyzed   by   an   iron   complex,   the   pincer   complex   (iPr-­‐PNP)Fe(H)Br(CO),  in  the  presence  of  catalytic  base,  is  reported.  A  wide  range  of  (hetero)aromatic  and  aliphatic  ni-­‐ triles  are  hydrogenated  to  the  corresponding  secondary  imines  under  mild  conditions.     KEYWORDS:  Iron,  nitriles,  secondary  imines,  hydrogenation,  pincer.  

Catalytic   hydrogenation   of   nitriles   constitutes   an   important   methodology  in  industry  and  academia.  Imines  and  amines  that   are   generally   formed   serve   as   important   intermediates   and   pre-­‐ cursors  in  the  synthesis  of  various  natural  products,  agrochemi-­‐ cals,   dyes,   pigments,   polymers   and   pharmaceuticals.1   However,   nitrile   hydrogenation   often   leads   to   mixtures   of   primary-­‐,   sec-­‐ ondary-­‐  and  even  tertiary-­‐  amines  via  imine  intermediates,  pre-­‐ senting   crucial   selectivity   issues   (Scheme   1).2   Therefore   the   dis-­‐ covery  of  a  catalyst  for  selective  hydrogenation  of  nitrile  to  either   of  these  products  is  desirable.  

           

Berke’s   group   reported   homogeneous   hydrogenation   of   nitriles   to  form  secondary  imines  as  major  products  using  molybdenum   and   tungsten   amides   bearing   the   so-­‐called   “MACHO”   PNP   pin-­‐ cer   ligand.18   These   reactions   proceed   at   high   temperature   and   pressure  (140  0C,  60  bar  H2),  and  high  catalyst  loadings  (5  mol%),   resulting  in  a  mixture  of  primary  amine,  intermediate  imine  and   secondary   imine   (major)   products,   while   selectivity   towards   secondary  imine  was  obtained  only  at  low  conversions.  The  only   hydrogenation   of   nitriles   to   secondary   imines   catalyzed   by   a   base-­‐metal  complex  was  reported  by  García  using  a  nickel  cata-­‐ lyst.19  That  system  requires  high  temperatures  (140-­‐180  0C)  and  is   limited   to   mono-­‐   and   dicyano-­‐   benzene   derivatives.   To   our   knowledge,  homogeneous  hydrogenation  of  nitriles  to  selectively   form  secondary  imines  catalyzed  by  iron  was  not  reported  so  far.  

Scheme  1.  Possible  products  in  nitrile  hydrogenation.  

  Conventional  methods  for  reduction  of  nitriles  involve  stoichio-­‐ metric   amounts   of   metal   hydrides,   or   hydrosilanes.3   Unfortu-­‐ nately,  these  routes  are  not  environmentally  benign  as  they  pro-­‐ duce   copious   waste.   Heterogeneous   catalysts   based   on   Co,   Ni   and   Pd,   commonly   used   for   nitrile   hydrogenation   in   industry,4   suffer  from  low  selectivity  towards  a  particular  product  and  low   functional   group   tolerance.   Typically,   homogeneous   catalysts   based  on  precious  metals  such  as  Ru,  Rh,  Ir,  and  Re  are  applied   in  the  hydrogenation  of  nitriles.5-­‐7     Replacement   of   precious   metal-­‐based   catalysts   by   complexes   of   earth   abundant,   low-­‐toxicity   first   row   base-­‐metals   is   a   topic   of   much   current   interest.8   Indeed,   recent   years   have   witnessed   much   progress   in   the   development   of   homogeneous   catalysts   based  on  earth-­‐abundant  base-­‐metals.9-­‐12  Of  prime  interest  is  the   use  of  iron  complexes  since  iron  is  generally  less  toxic  than  noble   metals  and  it  is  the  most  abundant  metal  on  the  earth  crust.   Iron   catalyzed   hydrogenation   of   various   substrates13   including   esters14   and   amides15   was   reported   by   a   few   groups,   including   ours.   Selective   catalytic   hydrogenation   of   nitriles   to   primary   amines   by   iron   complexes   (Figure   1)16,   as   well   as   by   Mn10a   and   Co12i  complexes,  was  also  demonstrated.   The  nitrile  group  is  an  important  functionality  in  various  natural   and   synthetic   organic   compounds,   including   pharmaceuticals,   and   it   can   be   further   processed   by   catalytic   hydrogenation   or   hydrolysis.17   In  addition  to  the  possibility  of  its  hydrogenation  to   form   primary   amines,   an   interesting   but   challenging   goal   is   the   direct   hydrogenation   to   selectively   form   secondary   imines.  

 

Figure  1.  Fe-­‐based  catalysts  for  homogeneous  nitrile  hydrogena-­‐ tion/hydrogenative  cross-­‐coupling  with  amine.   In   fact,   even   reports   on   precious   metal-­‐catalyzed   selective   hy-­‐ drogenation   of   nitriles   to   secondary   imines   are   rare.   Sabo-­‐ Etienne   observed   formation   of   N-­‐benzylidene-­‐1-­‐ phenylmethaneamine   during   the   hydrogenation   of   benzonitrile   in   the   absence   of   a   solvent   catalyzed   by   a   Ru   system.5b   Our   group,  and  recently  Prechtl  and  coworkers,  reported  hydrogena-­‐ tion   and   hydrogenative   coupling   of   nitriles   and   amines   to   give   secondary   self-­‐coupled   imines   and   cross-­‐imines   as   major   prod-­‐ ucts,  by  Ru-­‐PNN20a  and  Ru-­‐PNP20b  catalysts,  respectively.     Very   recently   we   reported   the   hydrogenative   cross-­‐coupling   of   nitriles   and   amines   to   form   secondary   aldimines   under   mild   conditions   (10-­‐20   bar   H2,   60   °C)   using   the   complex   Fe(iPr-­‐ PNP)(H)Br(CO)  (1)  in  the  presence  of  a  catalytic  amount  of  base   (Figure   1).21   Herein   we   employ   complex   1   and   catalytic   base   for   the   selective   hydrogenation   of   nitriles   to   secondary   aldimines.   The   reaction   proceeds   under   relatively   mild   conditions   (90°C,   30   bar  H2).  

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Catalytic   hydrogenation   of   benzonitrile   using   complex   1   to   give   selectively  N-­‐benzyl  benzaldimine  was  initially  chosen  as  a  mod-­‐ el   system.   The   influence   of   temperature,   hydrogen   pressure,   various  additives,  and  different  solvents  was  examined.  Selected   optimization   experiments   are   shown   in   Table   1.   Using   NaHBEt3   (1   mol%),   and   complex   1   (1   mol%)   under   60   bar   H2   at   65   °C   in   THF,  complete  conversion  of  benzonitrile  was  observed  after  38h       Table   1.   Optimization   of   the   reaction   conditions   for   the   hydrogenation  of  benzonitrile  catalyzed  by  1.  

     

En-­‐ a try  

Solvent  

1   2   3   4   5   6   7   8   9   10   11   12   c 13   14  

THF   THF   THF   THF   THF   THF   THF   Dioxane   C6H6   EtOH   EtOH   C6H6   iPrOH   C6H6  

Additives   (mol%)  

Time   (h)  

NaHBEt3  (1)   NaHBEt3  (1)   NaHBEt3  (1)   KHMDS  (1)   tBuOK(1)   tBuOK(1)   -­‐   tBuOK  (1)   tBuOK    (1)   tBuOK  (1)   tBuOK(1)   tBuOK(1)   tBuOK    (1)   tBuOK(1)  

38   20   20   10   10   5   10   10   10   10   5   5   5   18  

Tem p   (°C)   65   90   135   90   90   90   90   90   90   90   90   90   90   90  

H2     (ba r)   60   60   60   60   60   60   60   60   60   60   60   60   60   30  

b  

Conv (%)  

>99   >99   >99   84   >99   >99   00   >99   >99   >99   >99   >99   >99   >99  

Yield b  

(%)   64   98   71   40   97   53   00   96   98   98   97   98   46   93  

a

Conditions:   benzonitrile   (1   mmol),   1   (0.01   mmol)   additive   (1   equiv.   b relative  to  1),  and  solvent  (2  mL),  heated  in  an  autoclave.   yields  and   conversions  determined  by  GC-­‐MS  analysis  using  m-­‐xylene  as  inter-­‐ nal   standard.   Differences   in   conversions   of   benzonitrile   and   yields   of   N-­‐benzylidenebenzylamine   indicate   formation   of   benzaldimine   and   its   trimerised   N,N-­‐di(phenylmethylidene)phenylmethanediamine   C product.   53%  benzylamine  formation  was  observed.    

(Table  1,  entry  1)  as  revealed  by  GC-­‐MS.  Surprisingly,  no  primary   benzylamine,   or   dibenzylamine   were   detected   by   GC-­‐MS.   N-­‐ benzyl   benzaldimine   was   obtained   in   64%   yield.   The   partially   hydrogenated   product   benzaldimine   was   also   detected   by   GC-­‐ MS,  appearing  as  a  broad  signal  along  with  its  trimerized  prod-­‐ uct   N,N-­‐di(phenylmethylidene)phenylmethanediamine   (hydro-­‐ benzamide)   (Scheme   2).22   The   hydrobenzamide   was   character-­‐ ized  by  1H  NMR,  showing  a  typical  resonance  shift  at  δ  =  5.7  ppm   for  the  methyne  proton  and  at  8.3  ppm  for  the  imine  CH  proton   in   a   1:2   ratio.   In   the   13C{1H}   NMR   spectra,   the   methyne   carbon   resonates   at   δ   =   92.7   ppm   and   the   imine   carbon   at   δ   =   160.7   ppm   (see  Supporting  Information  (SI)).                 Scheme   2.   Products   detected   by   GC-­‐MS   and   1H   NMR   in   the   hydrogenation   of   benzonitrile   at   65°C   catalyzed   by   1   (Table   1,   entry  1).     Significantly,   increasing   the   temperature   to   90   °C   under   analo-­‐ gous   reaction   conditions   resulted   in   99%   consumption   of   ben-­‐ zonitrile,  yielding  98%  of  N-­‐benzyl  benzaldimine  after  20  h  (Ta-­‐ ble  1,  entry  2).  Although  benzylamine  was  not  detected,  it  is  like-­‐ ly   formed   as   an   intermediate,   followed   by   its   attack   on   the   in-­‐ termediate   imine   to   form   a   gem-­‐diamine   intermediate   which   liberates   ammonia   to   yield   the   desired   secondary   aldimine,   as  

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shown  in  Scheme  1.    It  is  also  noteworthy  that  no  hydrogenation   of  the  product  imine  took  place.  The  selectivity  towards  the  sec-­‐ ondary  imine  depends  strongly  on  the  reaction  temperature  and   pressure.  At  higher  temperature  (135  °C)  the  selectivity  dropped   and   a   lower   yield   of   N-­‐benzylidenebenzylamine   (71%)   was   ob-­‐ tained  (Table  1,  entry  3)  under  otherwise  the  same  conditions.     Exploring   the   effect   of   various   additives,   KHMDS   and   tBuOK   were  employed  under  similar  reaction  conditions.  Using  the  base   KHMDS  (1  mol%),  a  lower  yield  of  N-­‐benzyl  benzaldimine  (40%)   was  obtained,  in  comparison  to  when  NaHBEt3  was  used  (Table   1,  entry  4).  tBuOK  turned  out  to  be  the  best  additive,  resulting  in   97%  yield  of  N-­‐benzyl  benzaldimine  after  just  10  h  under  analo-­‐ gous   conditions   (Table   1,   entry   5).   In   the   absence   of   base,   em-­‐ ploying  pre-­‐catalyst  1  (1  mol%)  no  hydrogenation  of  benzonitrile   took  place  (Table  1,  entry  7),  indicating  that  one  equivalent  of       Table  2.  Hydrogenation  of  nitriles  to  secondary  imines  cat-­‐ alyzed  by  1.       En-­‐ a try  

Substrate  

Product  

1  

 

2  

c

b

b

Time   (h)  

Conv   (%)  

Yield   (%)  

 

1   mol %   1  

99  

97  

 

 

2  

99  

93  

3  

c

 

 

1  

99  

91  

4  

d

 

 

2  

18  

81  

52  

5  

d

 

 

1  

24  

>99  

79  

6  

d

 

 

4  

36  

>99  

56  

7  

d

 

 

4  

36  

59  

28  

8  

 

 

4  

14  

>99  

99  

9  

 

 

4  

12  

>99  

99  

10  

d

 

 

4  

16  

>99  

70  

11  

d

 

 

4  

14  

80  

61  

12  

 

 

8  

36  

61  

61  

13  

 

 

8  

36  

32  

32  

14  

 

 

8  

36  

69  

69  

15  

 

 

8  

36  

11  

11  

a

Conditions:   benzonitrile   (1-­‐0.125   mmol),   1   (0.01   mmol),   tBuOK   (1   equiv.   relative   to   1),   and   2   ml   C6H6   (1   mL   for   4   mol%   and   8   mol%   cat   b loading),  heated  in  an  autoclave  at  90  °C  under  30  bar  H2.   yields  and   1 conversions   determined   by   GC-­‐MS   and   H   NMR   analysis   using   m-­‐ c d xylene,   or   toluene   as   internal   standard.   isolated   yield.   Differences   in   conversions   of   nitriles   and   yields   of   secondary   imines   indicate   formation   of   partially   hydrogenated   intermediate   imines   and   their   trimerised  products.    

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ACS Catalysis base   (or   NaHBEt3)   (relative   to  1)   is   required  to   generate   the   ac-­‐ tive   catalyst.   Regarding   solvent   optimization,   dioxane,   benzene   or   EtOH   all   gave   exclusively   N-­‐benzylidenebenzylamine   (98%)   in  less  than  10  h  using  1  (1  mol%)  and,  tBuOK  (1  mol%)  at  90  °C   and  60  bar  H2  (Table  1,  entries  8-­‐12).  However,  using  isopropanol   as   solvent,   53%   of   benzylamine   formation   was   observed   along   with   N-­‐benzylbenzaldimine   (46%)   (Table   1,   entry   13)   after   5   h   under  otherwise  similar  conditions.  Gratifyingly,  lowering  the  H2   pressure   to   30   bar   in   the   presence   of   tBuOK   (1   mol%)   and   1   (1   mol%)   using   benzene   as   solvent   furnished   93%   N-­‐benzyl   ben-­‐ zaldimine  (Table  1,  entry  14)  in  less  than  18  h  at  90  °C.     Using   the   optimized   reaction   conditions   (C6H6,   90   °C,   30   bar   H2,   1   mol%   tBuOK   and   1   mol%   1),   the   generality   of   this   iron-­‐ catalysed   hydrogenation   of   nitriles   was   explored.   As   shown   in   Table   2,   benzonitriles   bearing   electron-­‐donating   substituents   at   the   para   positions,   including   4-­‐methoxybenzonitrile,   4-­‐ methylbenzonitrile,   4-­‐N,N-­‐   dimethylbenzonitrile,   and   meta-­‐ substituted   3-­‐methylbenzonitrile   were   hydrogenated   to   their   corresponding   secondary   aldimines   in   excellent   conversions   with   good   selectivities   (Table   2,   entries   1-­‐4).   Catalytic   hydro-­‐ genation   of   benzonitriles   bearing   electron   withdrawing   substitu-­‐ ents  at  the  para  positions,  including  4-­‐fluorobenzonitrile  and  4-­‐ chlorobenzonitrile,   also   afforded   selectively   the   corresponding   secondary  imines,  although  higher  catalyst  loading  (4  mol%)  was   required  in  the  case  of  the  latter.  No  hydro-­‐dehalogenation  was   observed  (Table  2,  entries  5  and  8).   However,   the   meta-­‐   and   ortho-­‐   substituted   3-­‐fluorobenzonitrle   and   2-­‐fluorobenzonitrile   yielded   the   corresponding   secondary   imines   in   moderate   yields   (Table   2,   entries   6   and   7)   along   with   the   formation   of   43%   and   31%   of   partially   hydrogenated   inter-­‐ mediate   3-­‐fluorobenzaldimine   and   2-­‐fluorobenzaldimine,   re-­‐ spectively   which   appeared   as   their   trimeric   products,   as   shown   by   1H   NMR.   Hydrogenation   of   p-­‐bromobenzonitrile,   applying   1   (4  mol  %)  as  pre-­‐catalyst  and  4  mol%  tBuOK  in  THF  resulted  in   99%   yield   of   N-­‐(4-­‐   bromobenzylidene)-­‐1-­‐(4-­‐ bromophenyl)methaneamine   (Table   2,   entry   9),   showing   that   even   bromo   substituents   are   tolerated.   Hydrogenation   of   2-­‐ naphthonitrile  resulted  in  the  formation  of  N-­‐(naphthylidene)-­‐1-­‐ (naphthyl)methanamine   in70%   yield   after   16   h   (Table   2,   entry   10).     The   scope   of   the   reaction   was   further   probed   by   employing   the   heterocyclic   nitrile   3-­‐pyridinecarbonitrile,   furnishing   N-­‐(3-­‐ pyridinylmethylene)-­‐3-­‐pyridinemethanamine   in   61%   yield   after   14  h  (Table  2,  entry  11).     Catalytic   hydrogenation   of   aliphatic   nitriles   bearing   alpha   hy-­‐ drogen  atoms  is  more  challenging  due  to  potential  base-­‐induced   condensation   side   reactions.   In   addition,   aliphatic   imines   are   inherently  less  stable.  Employing  the  Fe-­‐PNP  complex  1,  catalytic   hydrogenation   of   aliphatic   nitriles   progressed   sluggishly   com-­‐ pared   to   aromatic   nitriles,   and   catalyst   loading   had   to   be   in-­‐ creased.  Thus,  valeronitrile  and  butyronitrile  were  hydrogenated   to   the   corresponding   secondary   imines   in   61%   and   32%   yield,   respectively,   using   8   mol%   catalyst   1   and   NaHBEt3   (8   mol%)   under  30  bar  H2  at  90  °C  (Table  2,  entries  12  and  13).  Hydrogena-­‐ tion   of   the   secondary   alkyl   nitrile   cyclohexylcarbonitrile   resulted   in  formation  of  the  corresponding  secondary  imine  in  69%  yield   (Table   2,   entry   14).   Using   isobutyronitrile   under   similar   condi-­‐ tions,   only   11%   conversion   to   the   corresponding  secondary   imine   was   noticed   (Table   2,   entry   15).   The   expected   lower   stability   of   the  generated  alkyl  imine  intermediate  might  be  a  reason  for  the   inferior  performance.   Regarding  the  mechanism  of  the  nitrile  hydrogenation,  we  have   previously   reported21   that   complex   1   reacted   with   1   equiv.   of   tBuOK   in   THF   at   room   temperature   forming   a   deprotonated   amido   complex   (iPr-­‐PNP)Fe(H)(CO)   2   (Scheme   3)   and   reaction   with   1   equiv.   NaHBEt3   gives   the   cis-­‐dihydridocarbonyl   complex   (iPr-­‐PNP)Fe(H)2(CO)  3.  The  deprotonated  amido  complex  2  did  

not   react   with   benzonitrile   at   room   temperature   in   C6D6,   where-­‐ as  3  did  react  with  benzonitrile,  regenerating  the  amido  complex   2  and  benzaldimine.  Based  on  these  previously  observed  detailed   mechanistic   results,21   a   plausible   outer-­‐sphere   mechanism   is   depicted  in  Scheme  3.   Initially,  complex  2,  formed  by  reaction  of  base  with  complex  1,   adds   dihydrogen   by   metal–ligand   cooperation   to   generate   the   cis-­‐dihydrido   complex   3,   as   previously   reported.21   Complex   3   is   likely   in   equilibrium   with   the   unobserved  trans   dihydride   com-­‐ plex  3’,  which  is  believed  to  be  the  active  species.  The  imine  in-­‐ termediate   is   generated   by   hydride   and   proton   transfer   from   3’   to  the  nitrile  group,  either  in  a  concerted  or  stepwise  fashion  and   3’   is   converted   to   the   amido   complex   2.   Similarly,   in   another   catalytic   cycle   H2   is   transferred   to   the   imine   intermediate   to   form  the  primary  amine.  This  step  is  likely  the  rate  limiting  step,   otherwise   full   hydrogenation   to   the   amine   would   have   taken   place.   As   soon   as   the   primary   amine   is   formed,   nucleophilic   at-­‐ tack  by  the  amine  on  the  reactive  imine  intermediate  produces  a   gem-­‐diamine,  which  liberates  NH3  to  give  the  desired  secondary   imine  (Scheme  3).                  

                Scheme   3.   Plausible   mechanism   for   the   hydrogenation   of   nitriles  to  secondary  imine  catalyzed  by  iron.     In  conclusion,  we  have  presented  the  first  iron-­‐catalyzed  hydro-­‐ genation   of   nitriles   to   selectively   form   secondary   imines.   The   reaction   proceeds   at   relatively   low   temperature   and   pressure   (90   °C,   30   bar   H2),   under   apparently   neutral,   homogeneous   condi-­‐ tions,   using   the   pincer   complex   (iPr-­‐PNP)Fe(H)Br(CO)   1   and   a   base  (in  an  equimolar  amount  to  Fe).  No  products  of  full  hydro-­‐ genation  (primary  or  secondary  amines)  were  observed.  In  con-­‐ trast,   nitrile   hydrogenation   catalyzed   by   a   related   “MACHO”   ligand-­‐based   iron   system   developed   by   Beller16a   afforded   selec-­‐ tively   primary   amines,   providing   another   example   as   to   the   criti-­‐ cal  role  that  ligand  modification  may  have.  

AUTHOR INFORMATION Corresponding Author *E-­‐mail:  [email protected].    

Notes

The  authors  declare  no  competing  financial  interests.  

ASSOCIATED CONTENT Experimental  details  of  the  catalytic  experiments,  GC-­‐MS  data  of   hydrogenation  products,  and  NMR  spectra.  

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ACKNOWLEDGMENT     This  research  was  supported  by  the  European  Research  Council   (ERC   AdG   692775)   and   by   the   Kimmel   Center   for   Molecular   Design.  D.M.  holds  the  Israel  Matz  Professorial  Chair  of  Organic   Chemistry.   S.C.   thanks   the   Swiss   Friends   of   the   Weizmann   Insti-­‐ tute  of  Science  for  a  generous  postdoctoral  fellowship.  

REFERENCES (1)  (a)  Hadjipavlou-­‐Litina,  D.  J.;  Geronikaki,  A.  A.  Drug  Des.  Dis-­‐ covery   1998,   15,   199.   (b)   Adams,   J.   P.   J.   Chem.   Soc.   Perkin   Trans.   1   2000,  125-­‐139.  (c)  Gawronski,  J.;  Wascinska,  N.;  Gajewy,  J.  Chem.  Rev.   2008,  108,  5227-­‐5252.     (2)   Gomez,   S.;   Peters,   J.   A.;   Maschmeyer,   T.   Adv.   Synth.   Catal.   2002,  344,  1037-­‐1057.     (3)   (a)   Seyden-­‐Penne,   J.   Reductions   by   Alumino   and   Borohydrides   in   Organic   Synthesis,   2nd   ed.;   Wiley-­‐VCH:   Weinheim,   1997.   (b)   La-­‐ val,  S.;  Dayoub,  W.;  Favre-­‐Reguillon,  A.;  Berthod,  M.;  Demonchaux,   P.;   Mignani,   G.;   Lemaire,   M.   Tetrahedron   Lett.   2009,   50,   7005-­‐7007.   (c)   Corriu,   R.   J.   P.;   Moreau,   J.   J.   E.;   Pataud-­‐Sat,   M.   J.   Organomet.   Chem.   1982,   228,   301-­‐308.   (d)   Cabrita,   I.;   Fernandes,   A.   C.   Tetrahe-­‐ dron  2011,  67,  8183-­‐8186.  (e)  Bornschein,  C.;  Werkmeister,  S.;  Junge,   K.;   Beller,   M.   New   J.   Chem.   2013,   37,   2061-­‐2065.   (f)   Huckaba,   A.   J.;   Hollis,   T.   K.;   Reilly,   S.   W.   Organometalics   2013,   32,   6248-­‐6256.   (g)   Gandhamsetty,  N.;  Park,  J.;  Jeong,  J.;  Park,  S.-­‐Woo;  Park,  S.;  Chang,  S.   Angew.Chem.Int.Ed.   2015,   54,   6832-­‐6836.   (h)   Gandhamsetty,   N.;   Jeong,   J.;   Park,   J.;   Park,   S.;   Chang,   S.   J.   Org.   Chem.   2015,   80,   7281-­‐ 7287.   (i)   Geri,   J.   B.;   Szymczak,   N.   K.   J.   Am.   Chem.   Soc.   2015,   137,   12808-­‐12814.   (4)   (a)   Nishimura,   S.   Handbook   of   Hetergogeneous   Catalytic   Hy-­‐ drogenation   for   Organic   Synthesis;   John   Wiley   &   Sons:   New   York,   2001;  p  254.  (b)  Blaser,  H.-­‐U.;  Malan,  C.;  Pugin,  B.;  Spindler,  F.;  Stei-­‐ ner,  H.;  Studer,  M.  Adv.  Synth.  Catal.  2003,  345,  103.  (c)  Hegedus,  L.;   Mathe,  T.    Appl.  Catal.  A:  Gen.  2005,  296,  209.   (5)  (a)  Grey,  R.  A.;  Pez,  G.  P.;  Wallo,  A.  J.  Am.  Chem.  Soc.  1981,  103,   7536-­‐7542.   (b)   Reguillo,   R.;   Grellier,   M.;   Vautravers,   N.;   Vendier,   L.;   Sabo-­‐   Etienne,   S.   J.   Am.   Chem.   Soc.   2010,   132,   7854-­‐7855.   (c)   Gunana-­‐ than,   C.;   Hölscher,   M.;   Leitner,   W.   Eur.   J.   Inorg.   Chem.   2011,   2011,   3381-­‐3386.   (d)   Enthaler,   S.;   Addis,   D.;   Junge,   K.;   Erre,   G.;   Beller,   M.   Chem.-­‐Eur.   J.   2008,   14,   9491-­‐9494.   (e)   Werkmeister,   S.;   Junge,   K.;   Wendt,   B.;   Spannenberg,   A.;   Jiao,   H.;   Bornschein,   C.;   Beller,   M.   Chem.-­‐Eur.  J.  2014,  20,  4227-­‐4231.  (f)  Enthaler,  S.;  Junge,  K.;  Addis,  D.;   Erre,   G.;   Beller,   M.   ChemSusChem   2008,   1,   1006-­‐1010.   (g)   Li,   T.;   Bergner,  I.;  Haque,  F.  N.;  Zimmer-­‐De  Iuliis,  M.;  Song,  D.;  Morris,  R.   H.   Organometallics   2007,   26,   5940-­‐5949.   (h)   Adam,   R.;   Bheeter,   C.   B.;   Jackstell,   R.;   Beller,   M.   ChemCatChem   2016,   8,   1329-­‐1334.   (i)   Ad-­‐ am,  R.;  Alberico,  E.;  Baumann,  W.;  Drexler,  H.-­‐J.;    Jackstell,  R.;  Junge,   H.;   Beller,   M.   Chem.   Eur.   J.   2016,   22,   4991-­‐5002.   (j)   Takemoto,   S.;   Kawamura,  H.;  Yamada,  Y.;  Okada,  T.;  Ono,  A.;  Yoshikawa,  E.;  Mizo-­‐ be,   Y.;   Hidai,   M.   Organometallics   2002,   21,   3897-­‐3904.   (k)   Miao,   X.;   Bidange,   J.;   Dixneuf,   P.   H.;   Fischmeister,   C.;   Bruneau,   C.;   bois,   J.   L.   D.;  Couturier,  J.  L.  Chemcatchem.  2012,  4,  1911-­‐1916.   (6)   (a)   Yoshida,   T.;   Okano,   T.;   Otsuka,   S.   J.   Chem.   Soc.   Chem.   Commun.   1979,   870-­‐871.   (b)   Galan,   A.;   de   Mendoza,   J.;   Prados,   P.;   Rojo,  J.;  Echavarren,  A.  M.  J.  Org.  Chem.  1991,  56,  452-­‐454.  (c)  Chin,   C.  S.;  Lee,  B.  Catal.  Lett.  1992,  14,  135-­‐140.   (7)  Rajesh,  K.;  Dudle,  B.;  Blacque,  O.;  Berke,  H.  Adv.  Synth.  Catal.   2011,  353,  1479-­‐1484.     (8)   (a)   Albrecht,   M.;   Bedford,   R.;   Plietker,   B.   Organometallics   2014,   33,   5619-­‐5621.   (b)   Bullock,   R.   M.   Catalysis   without   Precious   Metals;  Wiley-­‐VCH:  Weinheim,  2010.   (9)  Recent  reviews:  (a)  Bauer,  I.;  Knolker,  H-­‐J.  Chem.  Rev.  2015,  115,   3170-­‐3387.   (b)   Morris,   R.   H.   Acc.   Chem.   Res.   2015,   48,   1494-­‐1502.   (c)   Chirik,   P.   J.   Acc.   Chem.   Res.   2015,   48,   1687-­‐1695.   (d)   Zell,   T.;   Milstein,   D.  Acc.  Chem.  Res.  2015,  48,  1979.  (e)  Chakraborty,  S.;  Bhattacharya,   P.;  Dai,  H.;  Guan,  H.  Acc.   Chem.   Res.  2015,  48,  1995-­‐2003.  (f)  McNeil,   W.;   Ritter,   T.   Acc.   Chem.   Res.   2015,   48,   2330-­‐2343.   (g)   Benito-­‐ Garagorri,  D.;  Kirchner  K.  Acc.  Chem.  Res.  2008,  41,  201-­‐213.  

Page 4 of 6

(10)   Mn   catalyzed   hydrogenation:   (a)   Elangovan,   S.;   Topf,   C.;   Fischer,   S.;   Jiao,   H.;   Spannenberg,   A.;   Baumann,   W.;   Ludwig,   R.;   Junge,  K.;  Beller,  M.  J.  Am.  Chem.  Soc.  2016,  138,  8809-­‐8814.  (b)  Kall-­‐ meier,   F.;   Irrgang,   T.;   Dietel   ,   T.;   Kempe,   R.   Angew.   Chem.   Int.   Ed.   2016,  55,  11806-­‐11809.  (c)  Elangovan,  S.;  Garbe,  M.;  Jiao,  H.;  Spannen-­‐ berg,  A.;  Junge,  K.;  Beller,  M.  Angew.  Chem.  Int.  Ed.  2016,  55,  15364-­‐ 15368.  (d)  Espinosa-­‐Jalapa,  N.  A.;  Nerush,  A.;  Shimon,  L.  J.  W.;  Leitus,   G.;  Avram,  L.;  Ben-­‐David,  Y.;  Milstein,  D.  Chem.  Eur.  J.  2016,  22,  DOI:   10.1002/chem.201604991.   (11)   Mn   catalyzed   conjugate   addition   of   non-­‐activated   nitriles:   Ne-­‐ rush,  A.;  Vogt,  M.;  Gellrich,  U.;  Leitus,  G.;  Ben-­‐David,  Y.;  Milstein,  D.   J.  Am.  Chem.  Soc.  2016,  138,  6985-­‐6997.   (12)  Selected  examples  of  Co  catalyzed  hydrogenation:  (a)  Zhang,   G.;   Scott,   B.   L.;   Hanson,   S.   K.   Angew.   Chem.,Int.   Ed.   2012,   51,   12102-­‐ 12106.   (b)   Zhang,   G.;   Vasudevan,   K.   V.;   Scott,   B.   L.;   Hanson,   S.   K.   J.   Am.  Chem.  Soc.  2013,  135,  8668-­‐8681.  (c)  Rösler,  S.;  Obenauf,  J.;  Kem-­‐ pe,   R.   J.   Am.   Chem.   Soc.   2015,   137,   7998-­‐8001.   (d)   Lin,   T.-­‐P.   ;   Peters,   J.   C.  J.  Am.  Chem.  Soc.  2014,  136,  13672-­‐13683.  (e)  Yu,  R.  P.;  Darmon,  J.   M.   ;   Milsmann,   C.;   Margulieux,   G.   W.;   Stieber,   S.   C.   E.;   DeBeer,   S.;   Chirik,  P.  J.  J.  Am.  Chem.  Soc.  2013,  135,  13168-­‐13184.  (f)  Korstanje,  T.   J.;   van   der   Vlugt,   J.   I.;   Elsevier,   C.   J.;   de   Bruin,   B.   Science   2015,   350,   298-­‐302.  (g)  Jeletic,  S.  M.;  Mock,  M.  T.;  Appel,  A.  M.;  Linehan,  J.  C.   J.   Am.   Chem.   Soc.   2013,   135,   11533-­‐11536.   (h)   Federsel,   C.;   Ziebart,   C.;   Jackstell,  R.;  Baumann,  W.;  Beller  M.  Chem.  Eur.  J.  2012,  18,  72-­‐75.  (i)   Mukherjee,  A.;  Srimani,  D.;  Chakraborty,  S.;  Ben-­‐David,  Y.;  Milstein,     D.  J.  Am.  Chem.  Soc.  2015,  137,  8888-­‐8891.  (j)  Srimani,  D.;  Mukherjee,   A.;  Goldberg,  A.  F.;  Leitus,  G.;  Diskin  Posner,  Y.;  Shimon,  L.  J.;  Ben-­‐ David,  Y.;  Milstein,  D.  Angew.  Chem.,  Int.  Ed.  2015,  54,  12357-­‐12360.   (13)  Selected  examples  of  Fe  catalyzed  hydrogenation:  (a)  Bart,  S.  C.;   Lobkovsky  E.;  Chirik,  P.  J.  J.  Am.  Chem.  Soc.,  2004,  126,  13794-­‐13807.   (b)  Yu,  R.  P.;  Darmon,  J.  M.;  Hoyt,  J.  M.;  Margulieux,  G.  W.;  Turner,   Z.  R.;  Chirik,  P.  J.  ACS  Catal.  2012,  2,  1760-­‐1764.  (c)  Srimani,  D.;   Diskin-­‐Posner,  Y.;  Ben-­‐David,  Y.;  Milstein,  D.  Angew.  Chem.,  Int.  Ed.   2013,  52,  14131-­‐14134.  (d)  Langer,  R.;  Leitus,  G.;  Ben-­‐David,  Y.;  Mil-­‐ stein,  D.  Angew.  Chem.,  Int.  Ed.  2011,  50,  2120-­‐2124.  (e)  Langer,  R.;   Diskin-­‐Posner,  Y.;  Leitus,  G.;  Shimon,  L.  J.  W.;  Ben-­‐David,  Y.;  Mil-­‐ stein,  D.  Angew.  Chem.,  Int.  Ed.  2011,  50,  9948-­‐9952.  (f)  Lagaditis,  P.   O.;  Sues,  P.  E.;  Sonnenberg,  J.  F.;  Wan,  K.  Y.;  Lough,  A.  J.;  Morris,  R.   H.  J.  Am.  Chem.  Soc.  2014,  136,  1367-­‐1380.  (g)  Zuo,  W.;  Lough,  A.  J.;  Li,   Y.  F.;  Morris,  R.  H.  Science  2013,  342,  1080-­‐1083.  (h)  Fleischer,  S.;   Zhou,  S.;  Junge,  K.;  Beller,  M.  Angew.  Chem.,  Int.  Ed.  2013,  52,  5120-­‐ 5124.  (i)  Gorgas,  N.;  Stöger,  B.;  Veiros,  L.  F.;  Kirchner  K.  ACS  Catal.   2016,  6,  2664−2672.  (j)  Marcos,  R.;  Xue,  L.;  Sanchez-­‐de-­‐Armas,  R.;   Ahlquist,  M.  S.  G.  ACS  Catal.  2016,  6,  2923−2929.  (k)  Chakraborty,  S.;   Lagaditis,  P.  O.;  Förster,  M.;  Bielinski,  E.  A.;  Hazari,  N.;  Holthausen,   M.  C.;  Jones,  W.  D.;  Schneider,  S.  ACS  Catal.  2014,  4,  3994−4003.  (l)   Chakraborty,  S.;  Brennessel,  W.  W.;  Jones,  W.  D.  J.  Am.  Chem.  Soc.,   2014,  136,  8564-­‐8567.  (m)  Casey,  C.  P.;  Guan,  H.  J.  Am.  Chem.  Soc.,   2007,  129,  5816-­‐5817.  (n)  Federsel,  C.;  Boddien,  A.;  Jackstell,  R.;  Jen-­‐ nerjahn,  R.;  Dyson,  P.  J.;  Scopelliti,  R.;  Laurenczy,  G.;  Beller,  M.  An-­‐ gew.  Chem.,  Int.  Ed.,  2010,  49,  9777-­‐9780.  (o)  Ziebart,  C.;  Federsel,  C.;   Anbarasan,  P.;  Jackstell,  R.;  Baumann,  W.;  Spannenberg,  A.;  Beller,   M.  J.  Am.  Chem.  Soc.  2012,  134,  20701-­‐20704.  (p)  Zell,  T.;  Ben-­‐David,   Y.;  Milstein,  D.  Catal.  Sci.  Technol.  2015,  5,  822–826  and  references   therein.  (q)  Zhang,  Y.;  MacIntosh,  A.  D.;  Wong,  J.  L.;  Bielinski,  E.  A.;   Williard,  P.  G.;  Mercado,  B.  Q.;  Hazari,  N.;  Bernskoetter,  W.  H.   Chem.  Sci.  2015,  6,  4291-­‐4299.   (14)  (a)  Zell,  T.;  Ben-­‐David,  Y.;  Milstein,  D.  Angew.  Chem.,  Int.  Ed.   2014,   53,   4685-­‐4689.   (b)   Werkmeister,   S.;   Junge,   K.;   Wendt,   B.;   Al-­‐ berico,   E.;   Jiao,   H.;   Baumann,   W.;   Junge,   H.;   Gallou,   F.;   Beller,   M.   Angew.  Chem.,  Int.  Ed.  2014,  53,  8722-­‐8726.  (c)  Chakraborty,  S.;  Dai,   H.;  Bhattacharya,  P.;  Fairweather,  N.  T.;  Gibson,  M.  S.;  Krause,  J.  A.;   Guan,  H.  J.  Am.  Chem.  Soc.  2014,  136,  7869-­‐7872.     (15)   (a)   Garg,   J.   A.;   Chakraborty,   S.;   Ben-­‐David,   Y.;   Milstein,   D.   Chem.   Commun.   2016,   52,   5285-­‐5288.   (b)   Schneck,   F.;   Assmann,   M.;   Balmer,   M.;   Harms,   K.;   Langer,   R.   Organometallics   2016,   35,   1931-­‐ 1943.  c)  Rezayee,  N.  M.;  Samblanet,  D.  C.;  Sanford,  M.  S.  ACS  Catal.   2016,  6,  6377-­‐6383.   (16)   (a)   Bornschein,   C.;   Werkmeister,   S.;   Wendt,   B.;   Jiao,   H.;   Al-­‐ berico,   E.;   Baumann,   W.;   Junge,   H.;   Junge,   K.;   Beller,   M.   Nat.   Com-­‐ mun.  2014,  5,  4111.  (b)  Lange,  S.;  Elangovan,  S.;  Cordes,  C.;  Spannen-­‐

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ACS Catalysis berg,   A.;   Jiao,   H.;   Junge,   H.;   Bachmann,   S.;   Scalone,   M.;   Topf,   C.;   Junge,   K.;   Beller,   M.   Catal.   Sci.   Technol.   2016,   6,   4768-­‐4772.   (c)   Chakraborty,   S.;   Leitus,   G.;   Milstein,   D.   Chem.   Commun.   2016.   52,   1812-­‐1815.   (17)  Fleming,  F.  F.;  Yao,  L.;  Ravikumar,  P.  C.;  Funk,  L.;  Shook,  B.  C.   J.  Med.  Chem.  2010,  53,  7902-­‐7917.   (18)  Chakraborty,  S.;  Berke,  H.  ACS  Catal.  2014,  4,  2191-­‐2194.   (19)  Zerecero-­‐Silva,  P.;  Jimenez-­‐Solar,  I.;  G.  Crestani,  M.;  Arevalo,   A.;   Barrios-­‐Francisco,   R.;   J.   Garcıa   J.   Appl.   Catal.   A:   Gen.   2009,   363,   230-­‐234.     (20)  (a)  Srimani,  D.;  Feller,  M.;  Ben-­‐David,  Y.;  Milstein,  D.  Chem.   Commun.   2012,   48,   11853-­‐11855.   (b)   Choi,   J.-­‐H.;   Prechtl,   M.   H.   G.   ChemCatChem  2015,  7,  1023-­‐1028.     (21)   Chakraborty,   S.;   Leitus,   G.;   Milstein,   D.     Angew.   Chem.,   Int.   Ed.  2017,  56,  2074-­‐2078.   (22)  Chou,  C.-­‐H.;  Chu,  L.-­‐T.;  Chiu,  S.-­‐J.;  Lee,  C.-­‐F.;  She,  Y.-­‐T.  Tet-­‐ rahedron  2004,  60,  6581–6584.  

 

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