Organic nitrites deoxygenated in presence of tervalent phosphorus reagent

Boyer, J. H.

Woodyard, J. D.

English

NASA Technical Reports Server

1 
P 
b 
la Deoxygenation of Organic Nitrites 
lb 2 J. H. Boyer and J. D. Woodyard 
Contribution from the Chemistry Department 
Chicago Circle Campus 
,3.lid UnZversity of  Illinois 0 
CTChicago, Illinois 60680 
3 
4 
5 
Abstract : Tri-n-butyl- - and triphenylphosphins and triethylphos- 
phits transform benzyl and _s_ tert-butyl nitrite into the corres- 
ponding alcohol. 
in tri-n-butylphosphine - also produces the expected alcohol there- 
by supporting their formation in the deoxygenation o f  nitrites by 
tervalent phosphorus reagents, 
P y r o l y s i s  o f  benzyl and ___I_ tart-butyl hyponitrite 
c 
In an attempt to produce examples of the unknown alkoxy ni- 
trenes, the deoxygenation of  nitrite esters by tervalent phosphorus 
reagents was investigated .3 
been transformed into the corresponding alcohol by both tri-E- 
butyl- and triphenylphosphine and triethglphosphite as a phosphine 
oxide or triethylphosphate is The intermediacy of an 
Benzyl and - tert-butyl nitrite have 
alkoxy nitrene is not required; however, a hyponitrite ester, 
which mag be recognized as the formal dimer of an alkoxy nitrane, 
-.I 
5 is ~t probs.ble intermediate. 
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R ONOPX, 
I 
2. 
An i n i t i a l  nuc leoph i l i c  a t t a c k  by t e r v a l e n t  phosphorus upon 
6 
7 
0 
9 
t h e  te rmina l  n i t r i t e  oxygen i s  proposed (equat ion 1).6 
t e n p t s  t o  t r a p  t h e  monomeric n i t r e n e ,  which might have been p r o -  
Since a t -  
duced by d i s s o c i a t i o n  of  t h e  z w i t t e r i o n i c  adduct ' (equat ion Z ) ,  
through a d d i t i o n  t o  an o l e f i n i c  bond or by i n s e r t i o n  w i t h  a CH 
bond were unsuccessfu l  i t  is  t e n t a t i v e l y  assumed t h a t  an alkoxy 
n i t r e n e  i s  not  generated,  This evidence does n o t  r i go rous ly  ex- 
c lude cap tu re  of t h e  n i t r e n e  on formation o f  a n i t r i t e  e s t e r  mole- 
c u l e  i n  a r e a c t i o n  l ead ing  d i r e c t l y  t o  
t i o n  2) .  It i s  assumed, however, t h a t  
w i t h  another  n i t r i t e  e s t e r  molecule t o  
a hyponitri te-N-oxide (equa- 
the i n i t i a l  adduct combines 
b r ing  abou t  t h e  formation 
of' t h e  azoxy compound i n  a r e a c t i o n  r e q u i r i n g  e i t h e r  concerted o r  
s tspwise e l imina t ion  o f  a phosphine oxide (equat ion 3 ) .  Con- 
ce ivably  alkoxy r a d i c a l s  could be produced d i r e c t l y  by t h e  frag- 
mentation of' t h e  proposed, but unknown, hyponitri te-N-oxide 
e s t e r .  I n  an a l t e r n a t e  sequence a h y p o n i t r i t e  may r e s u l t  from 
deoxygenation of i t s  N-oxide and subsequently undergo l o s s  of 
n i t rogen  w i t h  t he  gene ra t ion  of alkoxy r a d i c a l s  (equat ions 4,s). 7 
Abst rac t ion  of  hydrogen f r o m  t h e  organophosphorus so lven t  then  
accounts f o r  t h e  formation o f  ths expected alcohol.8 
s t e p  had been independently estabLished i n  the formation o f  P t e r t -  
bu ty l  a lcohol  f r o m  the  te r t -butoxy r a d i c a l ,  i n  t u r n  produced from 
d i - t e r t - b u t y l  __. peroxide i n  t r i p h e n y l p h o ~ p h i n e ~  and has now been 
This l a s t  
i 
3 .  
confirmed by the t ransformat ion  o f  a u t h e n t i c  benzyl and - tekt-
bu ty l  h y p o n i t r i t e  i n  i n t o  benzyl and t e r t -  
P
10 
11 
12 
bu ty l  a l coho l  r e spec t ive ly .  
An alkoxy r a d i c a l  a l s o  combines with a phosphine t o  genera te  
an a l k y l  r ad ica l9  (equat ion 6 ) .  With this  e w l a n a t i o n  f o r  t he  
presence of  benzyl and - t e r t - b u t y l  r a d i c a l s ,  hydrogen a b s t r a c t i o n  
by one and e l imina t ion  by the  o t h e r  accounts for t h e  minor y i e l d s  
of toluene and i sobuty lene  r e s p e c t i v e l y  from benzyl and __I_ t e r t -  
b u t y l  n i t r f t e  (equat ions 7,8). Inso fa r  as butene-1 was not  de- 
t e c t e d  by t h e  formation o f  i t s  dibrornlde the  formatj.on o f  t h e  
- n-butyl r a d i c a l  (equat ion 6 )  i s  .doubtful.  
Both t h e  cleavage o f  t h e  benzyloxy r a d i c a l  i n t o  t h e  phenyl 
r a d i c a l  and formaldehyde and of t h e  te r t -butoxy r a d i c a l  i n t o  t h e  
methyl r a d i c a l  and acetone as we l l  as t h e  apparent  d i spropor t ion-  
a t i o n  of  t h e  benzyloxy r a d i c a l  i n t o  benzaldehyde and benzyl a lco-  
h o l  are e s t a b l i s h e d  r e a c t i o n s .  lo Detec t ion  of low-boiling and 
gaseous products  o ther  than  i sobuty lene  and/or o t h e r  o l e f i n s  was 
no t  attempted hers and evidence for t h e  formation of  e i t h e r  ben- 
zene o r  benzaldehyde was no t  found. The observat ion,  f rom a 
sepa ra t e  experiment, tha t  benzaldehyde does n o t  r e a c t  wi th  tri- 
- n-butylphosphine under comparable condi t ions  renders  t he  absence 
of  benzaldehyde formation from both benzyl n i t r i t e  and h y p o n i t r i t e  
i n  an organophosphorus so lvent  unresolved A s o l u t i o n  t o  the 
problem may r e q u i r e  an explana t ion  f o r  t h e  formation and i d e n t i -  
f i c a t i o n  of  h igh-boi l ing  o i l s  which con ta in  phosphorus and oxygen 
but no n i t rogen .  A s i m i l a r  h igh-bbi l ing f r a c t i o n  was obtained 
fron: t e r t - b u t y l  n i t r i t e  e 12 
4. 
With a m o l a r  excess o f  tr iphenylphosphine or t r i e thy lphos -  
p h i t e  a l o w e r  y i e l d  of I t a r t - b u t y l  a lcohol  w a s  obtained f rom d i -  
t e r t - b u t y l  p e r ~ x i d e . ~  
product ion o f  __. t e r t - b u t y l  r a d i c a l s  (equation 6 )  requi red  f o r  an 
This  w a s  a t t r i b u t e d  t o  an increase  i n  t h e  
inc rease  i n  hydrocarbon products .  I n  c o n t r a s t ,  a s l i g h t  inc rease  
i n  t h e  y i e l d  of' benzyl a lcohol  f r o m  benzyl n i t r i t e  i s  r e a l i z e d  
*+ when a molar  excess of t r i -n-butylphosphine  i s  used. As d e t e r -  
mined by y i e l d s  o f  alcohols produced the  l a t t e r  reagent  appears  
t o  be more e f f e c t i v e  than  t r iphenylphosphine or t r i e t h y l p h o s p h i t e  ' 
but less e f f e c t i v e  than  isooctane13 i n  donating hydrogen t o  an 
alkoxy r a d i c a l  produced under comparable cond i t ions .  
b 
13 
Experimental 
Deoxygenation o f  N i t r i t e s .  With s t i r r i n g ,  17.39 g (0.127 m )  
of  f r e s h l y  prepared and r e d i s t i l l e d  benzyl n i t r i t e  14,15 w a s  added 
dropwiso over a pe r iod  o f  2 hours t o  25.60 g (0.127 m) o f  t r i - n -  -
butylphosphine which had bean r igo rous ly  d r i e d  over calcium h y -  
l4,lS 
d r i d e .  By e x t e r n a l  cool ing  t h e  temperature o f  t h e  exothermic 
r e a c t i o n  was kept  below 15' dur ing  add i t ion  but w a s  then  allowed 
t o  r i s e  t o  room temperature f o r  continued s t i r r i n g  overnight .  
D i s t i l l a t i o n  of  t h e  r e a c t i o n  mixture under ordinary pressure  gave 
0.34 g (3% y i e l d )  o f  to luene ,  b . p ,  109 - 11l0, i r  and nmr absorp- 
t i o n  i d e n t i c a l  with t h a t  o f  an au then t i c  sample. 
Continued d i s t i l l a t i o n  a t  3 mm separa ted  a low-boiling f r a c -  
t i o n  (60 - 15so) from which 8.15 g (65% y i e l d )  o f  benzyl a lcohol ,  
b.p. 202 - 2 O 4 O  (1 a tm.) ,  was separated by r e d i s t i l l a t i o n ,  i r  and 
nmr s p e c t r a  i d e n t i c a l  w i t h  those obtained from au then t i c  m a t e r i a l .  
From a h igher  b o i l i n g  f r a c t i o n  (154; - 165O/3 mm.) 19-20  g (75% 
5.  
y i e l d )  of t r i -n-butylphosphine  oxide,  m . p .  '65 . 6 8 O ,  w a s  obtained 
a f t e r  r e d i s t i l l a t i o n ,  i r  and nmr s p e c t r a  i d e n t i c a l  w i t h  t hose  
obtained from a u t h e n t i c  m a t e r i a l .  F i n a l l y  2.02 g of  a high-  
b o i l i n g  o i l ,  190 - 210°/0.25 mm, and a p o t  res idue ,  0.35 g, were 
no t  i d e n t i f i e d .  
When t h e  r e a c t i o n  w a s  repeated w i t h  a mola r  excess o f  t r i - n -  -
S butylphosphine, t h e  y i e l d  o f  benzyl a l coho l  i n  t h e  r e a c t i o n  m i x -  
t u r e  w a s  es t imated t o  be 78% as determined from the  nmr absorp t ion  
a t  6 4.55 (benzyl ic  p ro tons ) .  1 
With t h e  s u b s t i t u t i o n  o f  t r i e t h y l p h o s p h i t e  f o r  t r i -n -bu ty l -  - 
phosphine about 30 pe rcen t  benzyl n i t r i t e  remained unreacted a f t e r  
hea t ing  t h e  r e a c t i o n  mixture under n i t rogen  a t  looo  f o r  2 days  and 
a 55% y i e l d  of  benzyl a l c o h o l  was obtained.  
cohol was obtained from a moderately exothermic r e a c t i o n  between 
The same y i e l d  o f  a l -  
benzyl n i t r i t e  and triphenylphosphino i n  benzene. Attempts t o  ob- 
t a i n  products  by i n s e r t i o n  o r  a b s t r a c t i o n  w i t h  CH bonds i n  hydro- 
carbon s o l v e n t s  or by a d d i t i o n  t o  t h e  C=C double bond i n  cyclo-  
hexene which might be c h a r a c t e r i s t i c  o f  benzyloxy n i t r e n e  were Y 
unsuccessful .  
With s t i r r i n g  29.60 g (0.287 m )  of' f r e s h l y  prepared and re -  
16 d i s t i l l e d  t e r t - b u t y l  ni t r i te ' '  was' added dropwisa over  a pe r iod  of  
2 hours  t o  61.00 g (0.302 m )  o f  t r i -n-butylphosphine  i n  a 250 r n l  
3-necked f l a s k  equipped t o  d e l i v e r  evolved gas i n t o  a s o l u t i o n  o f  
3 m l  o f  bromine i n  250 m l  o f  carbon t e t r a c h l o r i d e .  
temperature w a s  c a r e f u l l y  he ld  between 65 - 70° ( the re  does not  
appear t o  be a r e a c t i o n  a t  room temperature)  and s t i r r i n g  was 
The r e a c t i o n  
continued a t  t h i s  temperature overn ight .  By d i s t i l l i n g  a t  or- 
dinary p res su re  1.42 g of unreacted t e r t - b u t y l  n i t r i t e  w a s  
6 .  
recoversd and 8.18 g (43.5% y i e l d  based on recovered n i t r i t e )  of  
t e r t - b u t y l  a lcohol ,  b.p. 80°, w a s  c o l l e c t e d ,  i r  and nmr absorp- 
t i o n  i d e n t i c a l  w i t h  t ha t  obtained f r o m  an au then t i c  sample. Con- 
t inued  d i s t i l l a t i o n  gave 57.74 g (91% y i e l d )  o f  t r i -n-butylphos-   
phine oxide,  b.p. l82O/23 m, ir and nmr absorp t ion  i d e n t i c a l  w i t h  
t ha t  f r o m  au then t i c  materi.al, and 5.00 g o f  an u n i d e n t i f i e d  o i l ,  
1 b.p. 220 - 230°/23 
By d i s t i l l a t i o n  1.95 (5.5% y i e l d )  of  isobutylene dibromide, 
b.p. 144 - 150°, was i s o l a t e d  from t he  r e a c t i o n  between t h e  evolved 
gas,  i sobuty lene ,  and bromine i n  carbon t e t r a c h l o r i d e ,  6 1.90 
24 
(6 p ro tons )  and 6 3.88 (2  p r o t o n s ) ,  From t h e  nmr the  product was 
judged t o  be about 90% pure .  
P y r o l y s i s  -_.c___ o f a E o n i t r i t e s .  . ”  In  a 1 0  ml r.b. f l a s k  f i t t e d  w i t h  
a r e f l u x  condenser, 0.66 g (3.79 m o l e )  o f  _ur_ t e t - b u t y l  h y p o n i t r i t e ,  13 
was s l o w l y  mixed with 3.86 g (19.1 m o l e )  o f  t r i -n-butylphosphine  
while e x t e r n a l  c o n t r o l  kept  t h e  temperature nea r  5So (below SOo 
t h e  two l i q u i d s  appear t o  be immiscible) .  
hours a t  t h i s  temperature,  __ t e r t - b u t y l  a lcohol  was de tec t ed  i n  
35% y i e l d  by measuring peak a reas  i n  vpc f r o m  an SE-30 ten-foot  
column operated a t  60°. Standards f o r  comparison i n  c l a c u l a t i n g  
y i e l d  cons i s t ed  o f  prepared mixtures  o f  t r i -n-butylphosphine  and 
After s t i r r i n g  f o r  20 
- t -bu ty l  a lcohol .  Caution. -
t e r n a l  c o n t r o l  of the  r e a c t i o n  temperature,  t h e  mixture of -- t e r t -  
In  one experiment w i t h  inadequate  ex- 
b u t y l  h y p o n i t r i t e  and t r i -n-butylphosphine  became explos ive .  
In  a s i m i l a r  r e a c t i o n ,  0.1471 Q (0.608 m o l e )  o f  benzyl hypo- 
1 7  n i t r i t e ,  m.p .  4.4. - 4 6 O  and 0.5846 g (2.89 m o l e )  o f  t r i - n -  
butylphosphine were s t i r r e d  overnight  a t  room temperature.  The 
i n i t i a l l y  c l e a r  s o l u t i o n  became dark brown a f te r  24 h o u r s  and then  
I 
yellow. Benzy l  a lcohol  was de t ec t ed  i n  38.276 y i e l d  by vpc. Stan-  
dards  f o y  comparison i n  c a l c u l a t i n g  y i e l d  cons i s t ed  of  prepared 
mixtures of' t r i -n-butylphosphins   and benzyl a lcoho l ,  
J 
8. 
Reference s 
1. 
2, 
3 .  
5. 
-. 
6, 
( a )  FAnanc,al support  was received from NASA g r a n t  
14-012-004, ( b )  To whom i n q u i r i e s  should be s e n t ,  
To. JGR 
Department o f  C h s m i s t ~ y ,  West Texas S t a t e  Univers i ty ,  Canyon, 
Texas 79015. 
Aryl n i t r e n e s  have been assumed interraadiates  i n  t h e  deoxygen- 
a t i o n  of aromatic C-nitroso compounds by  t e r v a l e n t  phosphorus 
reagents  (G. Smolinsky and B. I. Feuer, J. Org. Chem., -9 31 
3882 (1966); R. J. Sundberg, J. Am. Chem. SOC.,  -3 88 3781 (1966);  
J. I. G. Cadogan and M. J, Todd, Chem. Comun,, 178 (1967)) .  
Triphsnyl  phosphine was found i n e r t  t o  n i t rosamines  (L. Horner 
and H. Hoffmann, AngeW, Chem. ,  - 68, 473 (1956)) .  
I s o l a t i o n  of e t h y l  n i t r i t e  from t he  r e a c t i o n  between o -d in i t ro -  
benzens and t r i s t h y l p h o s p h i t e  (J. I. G. Cadogan, D. 6. Sears  
and D. N, Smith, Chem. Cornnun., 491 (1966)) apparent ly  r e -  
q u i r e s  the escape of t h e  gaseous e s t e r  on f o m a t i o n .  
P. J, Bunyan and J. I. G. Cadogan, J, Chsm. Soc., 42 (1963) 
r e p o r t  t h e  formation o f  azoxybenzene du r ing  t h e  deoxygenation 
of nitrosobenzene b y  t r iphenylphosphi re .  Fu r the r  deoxygena- 
t i o n  by t h e  same reagent  g ives  azobenzene (L, Horner and H, 
Hoffmann, Angew. Chem, , _. 68, 473 (1956) ). 
Deoxygenation of  aromatic n i t r o s o  compounds has  been accounted 
f o r  by both nuc leoph i l i c  ( S .  I. G. Cadogan, M. Cameron-Wood, 
R.  K. Mack3.e and J. G. Sea r l e ,  J. Chem. SOC., 4831 (1965))  
and e l e c t r o p h i l i c  (L ,  Hornsr and HI Hoffmann, Angew, Chem. ,  
_1_ 68, 473 (1956))  a t t a c k  by t e r v a l e n t  phosphorus on n i t r o s o  
oxygen * 
7 .  
8. 
d 
9 .  
._ 
10. 
11 
12 
Tervalent  phosphorus i s  known t o  deoxygenate n i t r o u s  oxide 
(equat ion 5 )  (R.  F. Hudson, "S t ruc tu re  and Mechanism i n  
Organophosphorus Chemistry f I Academic Press ,  New York, 1965, 
pp. 191, 192 ) .  
Assuming tha t  a r a d i c a l  may a t t a c k  a t  t h e  phosphorus atom 
i n  a phosphine oxide (compare t h e  formation of nit roxicles  
f r o m  n i t r o s o  compounds and f r e e  radicals) ,  an a d d i t i o n a l  se- 
quence of r e a c t i o n s  l ead ing  t o  an a lcohol  can be v i s u a l i z e d :  
RO* f R,'PO -+ R ? I ' P ( O R ) O *  R, 'P(OR)OH * R3'P0 f ROE. 
Eliminat ion o f  i sobuty lene  from t h e  adduct between a phos- 
phine oxide and _u_. t e r t - b u t y l  a lcohol  would p a r t i a l l y  account 
f o r  t h e  lower y i e l d  of t e r t - b u t y l  a lcohol  i n  the  deoxygena- 
t i o n  o f  - t e r t - b u t y l  n i t r i t e  and p y r o l y s i s  of' t h e  h y p o n i t r i t e :  
(CH,),GOP(OH)R,' + (CH3)2C=CH2 f R 3 f P ( O H ) z .  S t a b l e  phos- 
phins  oxide hydra tes  a r e  known ( r e f .  7 ,  p .  282). 
1 
C ,  Walling, 0. H, Basedow and E. S. Savas, J. Am. Chem. SOC., 
82,  - 2181 (1960) repor ted  the  f o r n a t i o n  o f  - t e r t - b u t y l  a lcohol  
(16% y i e l d )  from t h e  - t e r t -butoxy r a d i c a l  and isobutane,  i s o -  
butylene,  neopentane, isopentane,  i sooc tane ,  octenes and t e -  
tramethylbutzne from the  - t e r t - b u t y l  r a d i c a l  i n  t h e  r e a c t i o n  
between d i - t e r t - b u t y l  peroxide and t r iphenylphosphine.  
P.  Gray and A .  W i l l i a m s ,  Chern. Rev., I_ 59, 239 (1959). 
The r e s i s t a n c e  of' benzaldehyde t o  t e r v a l e n t  phosphorus has 
been r epor t ed  (F. Ramirez, S. B. Rhatia and 6. P. Smith,  
Tetrahedron, 9, 2067 (1967) ) 
S. A .  Buckler, J. Am. Chem. SOC.,  8& 3093 (1962) i n v e s t i -  
gated t h e  r e a c t i o n  between equimolar q u a n t i t i e s  o f  d i - t e r t -  _u_ 
b u t y l  peroxide and t r i -n-buty lphosphinsz   It was assumed that 
10. 
* 
- 1  . .iv 
deoxygenation o f  t h e  in te rmedia te  te r t -butoxy r a d i c a l  ac- 
counted f o r  t h e  formation o f  t r i -n-butylphosphine  oxide i n  
unspec i f ied  y i e l d .  Another phosphorus con ta in ing  product  was 
de tec t ed  and cha rac t e r i zed  by unreported nmr and ir s p e c t r a l  
data and vpc. 
di-n-butylphosphonite - (equat ion 6 )  Other products  were not  
repor ted .  
It w a s  assigned the  s t r u c t u r e  o f  _I_ t e r t - b u t y l -  
13, H. Kiefer  and T ,  G. T r a y l o r ,  Tetrahedron L e t t e r s ,  6163 (1966); 
J. Am. Chem. Soc,, 89,  667 (1967) repor ted  an  89% y i e l d  o f  
Iu_ t e r t - b u t y l  a lcohol  during the p y r o l y s i s  o f  _uI t e r t - b u t y l  hyponi- 
t r i t e  i n  i sooc tane .  
d 
_. 
14. I?. Kornblun, R.  A .  Smlley, R .  X. Blackwood and I). C. I f f l a n d ,  . 
J. m. Chem. Soc., _. 77, 6269 (1955). 
15. Benzaldehyde, de t ec t ed  by nmr, appears  i n  samples o f  benzyl 
n i t r i t e  a f t e r  s to rage  f o r  a few days .  
for by a chain r e a c t i o n  w i t h  oxygen a s  the  i n i t i a t o r :  
This  may be accounted 
16. C .  S. Coe and T. F. Doumani, J. Am. Chem.  Soc., 70, 1516 
I (194%). 
17. J. R. Pa r t ing ton  and C.  C, Shah, J, Chem.  Soc., 2071 (1931). 
. 11. 


Deoxygenation of organic nitrites

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