Organometallics 1982,1,289-295
289
Reactions of (Si1ytamino)phosphines with Ketones and Aldehydes‘ David W. Morton and Robert H. Neilson” Department of Chemistty, Texas ChrisNan Universiv, Fort Worth, Texas 76129 Received JuW 2 1, 198 1 I
I
(Sily1amino)phosphinesincluding (Me3Si)zNPMez(I),MezSiCHzCHzSiMezNPMez (2), and Me3SiN(R)PMez (3, R = t-Bu; 4, R = Me) react smoothly with carbonyl compounds in dichloromethane via nucleophilic attack by phosphorus and [1,4]-silylmigration from nitrogen to oxygen. Thus, treatment of phosphine 1 with saturated ketones and aldehydes affords high yields of the new N-silylphosphinimines (Sa-h). Similarly, 2 reacts with acetone to form the 8-membered ring Me3SiN=PMez-CRR’-OSiMe3 product MezSiCHzCHzSiMezN=PMezCMez-O (6). With a,b-unsaturated carbonyl compounds, 1,4 addition occurs to yield the acyclic (from 1) or 10-membered cyclic (from 2) silyl enol ethers Me3SiN= PMezCHRCH=CR’OSiMe3 [7, R = R’ = H; 8, R = R’ = Me; 9, R, R’ = (-CH2-)3] and 1 MezSiCHzCHzSiMezN=PMezCHzCH=CMeO (10). The (N-alkyl-N-sily1amino)phosphines3 and 4 also react with carbonyl compounds, but, except for ~ - B U N = P M ~ ~ C ( C F ~ ) ~ (ll), O Sthe ~ Mproducts ~~ are phosphine oxides O=PMez-CRR’-OSiMe3 (13,R = H, R’ = Me; 14,R = R’ = Me; 15,R = H,R’ = Ph). Phosphine 3 reacts with methyl vinyl ketone to afford the unstable phosphinimine t-BUN= PMezCHzCH=CMeOSiMe3(16). Proton, lac, and 31PNMR spectroscopic data for this new series of compounds are reported.
.
I
Introduction Recent studies of (sily1amino)phosphines such as (Me3SQ2NPMe2have shown them to be easily prepared reagents which exhibit a rich and interesting derivative chemistry. Specifically there are three potential modes of reactivity in such systems: (a) nucleophilic attack by phosphorus; (b) nucleophilic attack by nitrogen; (c) electrophilic attack by silicon.
reaction at both phosphorus and silicon to afford the Pbromophosphinimines which ace important intermediates in the synthesis of alkyl-substituted phosphazene polymer~.~~~ The findings have led us into a more extensive investigation of the reactivity of (sily1amino)phosphinesespecially toward electrophilic organic substrates. A preliminary s t u d 9 has shown that treatment of (Me3Si),NPMe2 with either acetone or hexafluoroacetone gives high yields of novel phosphinimines (eq 4). These observations were Me
We have previously observed that a combination of pathways a and c is operative in the attempted synthesis of oxide (eq 1)3or ylide (eq 2)4 derivatives. In both cases, the isolated products are the isomeric N-silylphosphinimines resulting from [1,3]-silylmigrations. Similarly, the bromination of (sily1amino)phosphines (eq 315 involves
Ye
MesSiN=P-OSiMe3
I
-
(Me3Si)zNPMez t RzCO
:W = nucleophile; E = electrophile
Me Me
I
Me
(4)
R = Me, CF,
contrasted with the general lack of reactivity of phosphines with ketoness and with the oxidative reaction of (CF3)&0 with (Me3Si)zNPF2to give the cyclic phosphorane1° I I (Me3Si 12 NWC(CF3)zC(CF3)z0
(1)
Me Me
R
I I Me3SiN=P-C-OSiMea I 1 Me R
//
F
F
We report here some results of a more detailed study in which a representative series of (sily1amino)phosphines were treated with a variety of aldehydes and ketones including a,@-unsaturatedsystems. The reactions of (sily1amino)phosphineswith other types of organic compounds will be reported in subsequent papers. (5) Wisian-Neilson, P.; Neilson, R. H. Inorg. Chem. 1980, 19, 1875. (6) Wisian-Neilson, P.; Neilson, R. H. J . Am. Chem. Soc. 1980, 102,
2848.
(1) Presented in part at the Intemational Conference on Phosphorus Chemistry, Durham, NC, June 1981; Abstr. 176. (2) Taken in part from the PbD. Dissertation of D. W. Morton, Texas Christian Univereity, Fort Worth, TX, 1981. (3) Neileon, R. H.; Wisian-Neileon, P.; Wilburn, J. C. Inorg. Chem. 1980, 19, 413. (4) Wdburn, J. C.; Neilson, R. H. Inorg. Chem. 1979, 18, 347.
0276-7333/82/2301-0289$01.25/0
(7) Neilson, R. H.; Wisian-Neilson,P. J. Mucromol. Sci., Chem. 1981, A16, 425. (8) Neilson, R. H.; Goebel, D. W. J.Chem. Soc., Chem. Commun. 1979,
769. (9) Emsley, J.; Hall, D. “The Chemistry of Phosphorus”; Halsted Press: New York, 1976; Chapter 4. (IO) Gibson, J. A.; Rijschenthaler, C.-V.;Schmutzler, R. J. Chem. Soc., Dalton Tram. 1975,918.
0 1982 American Chemical Society
290 Organometallics, Vol. 1, No. 2, 1982
Morton and Neilson
Table I. Preparative and Analytical Data for New N-Silylphosphinimines preparative compd 5a 5b 5c ::b
5f 5gc 5h 6' 7 8 9 10' 11 13 14 15 16'
rx time N-P-Me
It
Mee
be
/
(7)
I
In spite of ita thermal instability, the exclusive formation of the ring-expanded product 6 (eq 6) does have mechanistic implications. In this case certainly, and perhaps in the others (eq 5), the silyl shift from nitrogen to oxygen must occur by an intramolecular pathway. Otherwise, acyclic oligomers would have been produced. The reaction times in Table I show the expected trends in reactivity of aldehydes and ketones. For example, the reaction with acetaldehyde is much faster than the reaction with acetone. The fluoro- and chloro-substituted acetones
Organometallics, Vol. 1, No. 2, 1982 291
Reactions of (Sily1amino)phosphines also react substantially faster than acetone itself, undoubtedly due to the enhanced electrophilicity of the haloacetones. These qualitative observations are consistent with a mechanism in which attack by phosphorus on the carbonyl carbon is the rate-determining step. A few other features of this general reaction (eq 5) are worthy of note. First, another possible mode of reactivity for the chloroacetones might have been attack by phosphorus on the CH2C1carbon to give a phosphonium salt; however, products resulting from this pathway were not observed. Second, in the case of biacetyl, reaction with phosphine 1 occurred at only one of the carbonyl groups to yield 5e even if an excess of 1 was employed. Third, the compounds 5f and 5g derived from chloroacetone and 1,3-dichloroacetone, respectively, are an interesting pair with regard to their spectral and physical properties. As indicated in Table I, compound 5f is distillable and can be purified by careful fractionation to remove any unreacted chloroacetone. The diastereotopic protons of the chloromethyl group give rise to an ABX pattern (X= in which the upfield half is clearly split into quartets with a coupling constant of 0.4 Hz. This coupling is assigned as a 4J between one of the CH2protons and those of the CH3group attached to the chiral carbon. Compound 5g was prepared in order to observe the ABX pattern without this long-range coupling. Indeed, spectra of the crude product 5g were obtained with the desired result. Attempted distillation of 5g, however, brought about elimination of Me,SiCl and the bulk of the material solidified into a white mass. Complete characterization of the solid was not accomplished, but the NMR data are consistent with the formation of oligomers of the type [-N=PMe2-C (OSiMe,) (CH2C1)CH2-I,. Similar reactions of cr,&unsaturated carbonyl compounds with (sily1amino)phosphines were studied to determine whether the addition would proceed in a 1,2 or 1,4 manner. The carbonyl compounds investigated were methyl vinyl ketone, acrolein, and 2-cyclohexen-1-one. In each case, 1,4 addition was the observed result (eq 8), leading to the formation of N-silylphosphinimines 7-9 containing silyl enol ether functional groups. Me
7, R = R’ = H 8, R = H, R = M e
Molecular models of the intermediate enolates (eq 9)
(9)
z
E
show that an intramolecular [1,6]-silylmigration is more easily accomplished when the configuration is 2,thus giving rise to the more abundant product 7(2).The E isomer may be formed by an intramolecular silyl migration in the enolate with E configuration, although the transition state for such a process has a rather strained geometry. Alternatively, it is possible that 7(E)is formed by an intermolecular silyl shift, as in the case of the reaction of 1 with 2-cyclohexen-1-one (eq 10). Measi \
r
9
It is interesting to note that the reaction of 1 with acrolein (and with methyl vinyl ketone) occurs almost instanteously, but the reaction with 2-cyanohexen-1-one requires about 38 h for completion. This marked contrast in reaction times (and molecular models) strongly suggests that the formation of 9 occurs via an intermolecular silyl migration as shown in eq 10. Methyl vinyl ketone reacts (eq 8) as rapidly with phosphine 1 as does acrolein. In this case, however, only a single silyl enol ether 8 is obtained. Although the actual configuration is uncertain, the rapidity of the reaction suggests an intramolecular silyl shift which would favor formation of the 2 isomer.
9,R = R‘= -CH ,CH,CH,-
Me3SiN=PMee
AH
Me330
The product of the acrolein reaction 7 is obtained as a mixture of isomers in a ratio of approximately 80% 2 and 20% E. These two configurations were distinguished in the lH NMR spectrum by the magnitudes of the vinylic coupling constants: 5.75 Hz for the cis protons of 7(2) and 11.91 Hz for the trans protons of ?(E). The product ratio was estimated from the 13C NMR spectrum by using the relative intensities of the corresponding vinylic and allylic carbon signals. Me3SiN=PMe2
Me
8 (2)
The cyclic (sily1amino)phosphine 2 also reacted with methyl vinyl ketone (eq ll),and the reaction progress was Me
Me G I N =PMez H\
\
2
10
monitored by NMR spectroscopy. If methyl vinyl ketone
292 Organometallics, Vol. 1, No. 2, 1982
Morton and Neilson Table 11. NMR Spectroscopic Dataa 'H NMR
compd MeaSiN=PMez
I
-OSiMe3
F3C-6
I
CF3
5a MeaSiN=PMez
I
Me -C--OSiMe3 I Me
5b Me3S,N=PMez
I I
Me-
C -@S#Me3
5c Me3SiN=PMez
I Ph --C-OSiMen H
5d
Me3SiN=Ph
e*
I
ME - C-OSiMea
I
5e
CHzCI
5f
MenS,N=
We2
I I CHzCI
CIHzC-
C-@SiMe3
5g MeaSiN=PMez
I -OSlMe3 c~ HzC2
/
\
I ti2c3
C2Hz
I c3n2
\c4/ H2
signal Me.SiN MeiSiO Me,P (F3C)2C F3C
6
0.07 0.34 1.60
Me,SiN Me,SiO Me,P Me,C Me,C
-0.02 0.17 1.30 1.41
Me,SiN Me,SiO MeP MeP MeC HC Me,SiN Me,SiO MeP MeP HC Ph
-0.03 0.28 1.39 1.45 1.49 3.94 -0.04 0.15 1.17 1.45 4.73 7.18-7.44
Me,SiN Me,SiO MeP MeP PCMe PCMe PCCMe PCCMe Me,SiN Me,SiO MeP MeP PCMe PCMe CHCl
0.03 0.21 1.27 1.39 1.69
CHCl CH,C1 Me,SiN Me,SiO Me ,P PCCH, PCCH, PCCH, Me ,SiN Me,SiO Me,P C' C'H, C3H, C4H,
JPH
I3CNMR JHH
0.4
3.51 1.14 17.77 79.84 123.10
12.6
0.4
4.16 2.40 12.97 24.02 73.54
12.6 12.6 0.4 12.3 12.3 15.0
4.8 0.4
6.8 6.8
12.6 12.6 10.7
0.4 12.6 12.2 14.3
0.6 0.6
2.35
o.ooc
0.4
0.24 1.32 1.35 1.59
12.2 12.3 13.3
0.5 0.5 0.4
3.91
4.5
4.06
6.4
11.5 0.4 11.5
0.03 0.29 1.47 3.9 4.10 -0.03 0.20 1.27
0.4 12.0 9.0 9.4
6
11.6 11.6
3.96 -0.08 11.67 15.57 16.41 68.24 3.86 -0.12 12.26 16.08 75.90 126.82 127.45 127.47 137.34 3.84 2.14 13.90 14.23 20.21 54.54 28.34 207.85 3.96 2.27 14.01 14.42 19.35 75.71
51.15 3.96 2.27 16.81 46.74 78.17 4.32 2.79 13.61 76.64 30.93 21.18 25.40
0.4 12.0
1.60-1.83 1.60-1.83 1.60-1.83
,lP NMR JPC
3.1
6
7.76
72.6 70.8 3.1
20.93
65.3 5.5 96.4 3.1
17.41
64.1 66.5 2.4 93.4 3.7
15.06
61.0 69.6 87.9 3.7 5.5 0.6 3.1
15.62
66.5 62.9 83.6 3.9 3.1
18.73
64.7 63.5 4.3 93.4
16.5 3.1
15.44
63.5 11.0 91.6 2.9
17.84
61.5 96.7 5.9 9.8
5h
6 Me3SiN =PMe2
I
Me,SiN Me,SiO SiCH, Me,P Me,C Me,C
-0.09 0.07 0.61d 1.29 1.34
Me,SiN Me,SiO Me,P PCH,
0.03 0.20 1.35 2.50
12.8 16.1
PCCH
4.47
4.8
PCCCH
6.25
4.9
0.4
1.97 0.49 11.09 13.26 25.30 73.62
12.0 13.4 0.4
7.9 1.2 7.9 5.7 5.7 1.2
5.5
20.50
65.3 5.5 83.0
3.61 -1.10 16.91 29.73
3.7 67.8 65.9
100.59
8.6
139.69
11.0
8.16
Organometallics, Vol. 1, No. 2, 1982 293
Reactions of (Sily1amino)phosphines Table I1 (Continued) 'H NMR
compd
signal
Me3SiN=PMez
I
MenSiN=
PMeZ
I MeSSiO,
,cHZ
/c=c Me
\H
8
9
PMez
I I
F3C -C-OSiMea CF3
11 O=PMeZ
I Me-C-OSIMea I 13 O=PMez
I
12.8 14.9
PCCH
4.92
5.5
PCCCH
6.20
4.8
Me,SiN Me,SiO Me,P PCH, PCCH
-0.03 0.21 1.24 2.30 4.32
0.4 12.3 15.6 5.4
1.78
5.4
0.04e 0.21 1.28 2.2-2.7 1.2-2.1 1.2-2.1 1.2-2.1
0.4
PCCCMe PCCCMe Me,SiN Me,SiO Me,P HC' H,C2 H,C3 H,C4 C5 IIC6 Me,SiN Me,SiO CH,SiN CH,SiO Me,P PCH, PCCH
PCCCMe PCCCMe Me,Si Me,C Me,C Me ,P (F3C)1C F3C Me# MeP MeP MeC HC
4.90 0.03e 0.26 0.39-0.90 0.39-0.90 1.40 2.42 4.35
5.1 1.2 11.9 8.1 11.9 1.2
7.5 7.5
