4732
COhlhlUNICATIONS TO I-Ethoxyphosphole 1-Oxide'
Sir We wish to report the synthesis of the very reactive heterocyclic phosphinic acid ester, 1-ethoxyphosphole 1-oxide (I) 2 , 3 The ester dimerizes too readily to allow its isolation, but it has been identified by its ultraviolet spectrum and by trapping i t as a DielsAlder adduct with cyclopentadiene The synthesis from 1-ethoxy-2-phospholene 1-oxide4is given below Br
N(CH3)z
THE
EDITOR
Vol S(i
sity decreases more slowly; apparently the anion tliinerizes less readily than the ester. 113th a 30-fold or lOO-fold excess of cyclopentadiene in ethanol a t 25', I reacts with a second-order rate constant of approximately (1.051. 'mole sec. to produce the Diels-Alder adduct, 11. This compound has been purified by column chroinatography over \Yoelm grade 1 alumina with elution by chloroform, followed by molecular distillation. . I nni. Calcd. for CllHI5O2P: C , (i2.S-L: FI, 7.19; P, 14.74. Fountl: C, (i2.50: H . 7.45; P, 14.4s. Principal infrared absorptions occur a t i3.22 (shoulder),:3.:32, (i.;32, 7.50,8.22 (broad), T L j (broad), lil.52 (broad), 11.72, 11.99, and 18.21 (broad) p The complicated n.m.r.spectrum of I1 is consistent with the structure assigned, although the stereocheinistry is uncertain.
11
Both the bromide and the dimethylamino compounds are oils, and although the structures are reasonable on the basis of spectral evidence neither has been obtained pure. The quaternary ammonium iodide, crystallized from ethanol-acetone, melts sharply a t 141-.-141.5°. .lnal. Calcd. for C Y H 1 Y I K 0 2 P C:, 32.65; H , 5.78; I , 38.33 ; K, 4.23 : P, 9.;36. Found : C , 32.T:j; H , 5.87: I , 38.40; S , 1.27:P, 9.35. The iodide was converted in solution to the corresponding chloride by shaking in water with silver chloride; the resulting salt has an extinction coefficient of less than 2 above 240 rnp. "hen the quaternary ammonium salt in 0 . ~ ~ ~ 1 1 8 - ~ l .lI . ~ ~solution ~ 1 0 4 ~in ~ ethanol is treated with sodium ethoxide (0.01 to 0.0017 *\I), it reacts a t 25' to produce a compound to which the structure I has been assigned; Amax 293 mp ( t 1050); the rate constant for the elimination is roughly IO' 1. h o l e sec. Conipound I (identified by ultraviolet absorption and rate of dimerization) may also be prepared from the bromide, although here the approximate rate constant for its formation is only :3 L m o l e sec. In ethanol, I undergoes a second-order reaction, with a rate constant a t 23' of 0.55 1. mole sec., and concorriitant disappearance of the absorption a t 2%3 inp. The rate of the dimerization is about the same in the presence of added potassium iodide, trimethylamine. acetic acid, or excess sodium ethoxide, although the reaction product tieconiposes in the presence of this last reagent. The phosphinate ester, I , is presumably saponified by aqueous alcoholic sodium hytlrositle. The ultraviolet maximum m p . and the optical denof the product is shifted to
I-Ethoxyphosphole 1-oxide is similar in its absorption 289 m p ( t spectrum to thiophene dioxide,," (A,, 1 2 3 0 ) ) , but is even more reactive than the latter. Research is continuing with the objective (among others) of preparing phosphinate esters with phosphorus a t a bridge position of bicyclic systems. (i, 1%' J Bailey a n d 1;.
W. C u r n m i n s , J A m < h e m .S'oc., 76, liJ:(P ! l i l d l )
D. A ~ J S H E R THEJ A M E S BRY.4ST C O S A h T LABORATORY HARVARD USIVERSITY 1'. H . WESTHEIMER CAMBRIDGE, xfASSACHUSETTS 02138 RECEIVED SEPTEMBER 17, 1964
Aliphatic Cyanates
Sir: 11-e wish to report the first synthesis of aliphatic cyanates. Reasonably stable cyanates, R-O--C=K, can be prepared if (1) the aliphatic group. K,is sufficiently bulky to prevent facile trimerization. and (2) the carbonium ion, K +, is of sufkiently high energy to minimize solvolysis (and rearrangement) of the cyanate under the conditions of synthesis. Thus 1 ,l-tiihydroxybicvclo[%.2.2]octane,ij-ethoxy-, L'.2.t.4-tetraiiiethylcyclobutan-l-ol, or neopentyl alco! hol, when treated successively with sodium hydride (or butyllithiuiii) arid c>-anogen chloride. yielded the corresponding cyanates I (4lCh, 111.1'. 155-15(jo), 11 (:iOCL. b.p. (i:3' ('0.1 inin.)), and 111 (4.4c&,,b.p. 1 2 3 ' ( I S.5 mm.)) .? OCN
OCN
OCN
OCiHs
OCN I
, 1 ) T h i i r e s e a r c h nab \ u p ~ ~t e~d> I,y i t h e Saticlnal Scipnce l'i,undatiirn t i n d e r G r a n t >- GP-20W ' 2 1 .4 n n r n h e r u f \ u h i t i t u t e r l 1 - p h e n y l p h c i \ p h r , l e i h a v e previoriily h ~ e n r e p u r t e d brit a r e r e l a t i i e l y u n r r a c t i b e I:. C . I x a v i t t . T .4 \ l a n u e l , a n d :I J u h n s o n J d i n ( ' h t , i i i .\oi . 61, : i I l i < [ I E H B r a y e a n d 1V H u h r l . ('hc i n i i i , l & o n d i , n l . 12.iO , I $l,iW , A 1V J o h n s < i n a n d J C ' f c h h y . J ( h r m .So< 2126 , l $ J I j l I , J R H e n d r i c k s o n , I< li S p e n g e r . anrl J J S i l n i . 7 ?i?oh?dro>j I.it1r~i.s. 1 7 7 ( l ! l t j l i , I 11 C a m p b e l l . I< C C i x , k w , n . a n d \ I I3 H o c k i n g C h i i n l i i , ! 1 1 I c I n I , .i.i'l r l l l ( i 2 r . C; S I l e d d y a n d C 1) R'ei,, J 0i.p. ('ht,riz , 28, 1852 I I t:i, PI-ellminary r e p o i t , desciihe t h i e e 1 ~ p h e n y l p h c l s p h o l e I ~ i ) x i d e > see l i 1- D o n a d i i i . L I t ~ ~ ~ ! t ~ z fADili, t o i i , 20, 49; [l!I,j!I), l i H f t h e A m e r i c a n C h e m i c a l S i x i e t y A t l a n t i c C i t y I J , Sept , l$ISll, p . lOOP '1, 1. F I a ~ b e r < ~ r K l t . HunKer. anrl P K i r t e . l'etroh?,irt>?i,19. liii:i 1 l!lli:il
I
I1
CH3 111
