Silacrowns, a New Class of Immobilizable Phase Transfer Catalysts

17 S i l a c r o w n s , a N e w C l a s s of I m m o b i l i z a b l e P h a s e

Downloaded by UNIV OF CALIFORNIA SANTA BARBARA on July 1, 2016 | http://pubs.acs.org Publication Date: July 2, 1982 | doi: 10.1021/bk-1982-0192.ch017

Transfer Catalysts BARRY ARKLES, WILLIAM R. PETERSON, JR., and KEVIN KING Petrarch Systems Research Laboratories, Bristol, PA 19007 Immobilized phase transfer catalysts can be expected to demonstrate the same advantages as other immobilized catalysts. The reactions are clean, the products are uncontaminated by catalysts, the catalyst i s reuseable. The desireable properties of phase transfer catalysts that must be maintained include their ability to facilitate certain organic syntheses, behave as ionophores, solubilize metal salts and act as complexing agents. Polymer bound phase transfer catalysts, both onium salt1,2,3,4 and crown ether have been reported. The polymer bound phase transfer catalysts appear to require two special conditions for optimum product turnover: a relatively long "spacer" group between the polymer and the catalytic center and a swollen polymer substrate. It has been recently reported that the use of silica gel for immobilization of onium salts reduces the importance of "spacer groups" for catalytic activity although they do modify the adsorptive capacity of the silica. Crown ethers have also been recently immobilized on s i l i c a . The system demonstrates an adsorptive capability for metal ions that may be useful i n metal ion chromatography. 5,6

7

8,9

A l l s i l i c a immobilized phase transfer catalysts previously reported involve two or more steps for the immobilization. Problems with preparations of this type include the difficulty in obtaining maximum functionality on the substrate and residual substrate bond intermediates which may interfere in final applications. The purpose of this work was to prepare'wellcharacterized functionalized phase transfer catalysts that could be immobilized on siliceous substrates i n a single step. As w i l l be shown the preparation of functionalized onium catalysts proceeds readily. The route to facile immobilization of crown ether was not so direct. Avenues for high yield chemistry employing accessible or economic intermediates were not available. A new class of crown ethers which are readily functionalized during synthesis was developed. We have designated them " s i l a crowns". This report concentrates upon the properties and characterization of these new phase transfer catalysts.

0097-6156/82/0192-0281 $6.00/0 © 1982 American Chemical Society Miller; Chemically Modified Surfaces in Catalysis and Electrocatalysis ACS Symposium Series; American Chemical Society: Washington, DC, 1982.

282

CHEMICALLY MODIFIED SURFACES

Since 1967 when C. Pedersen discovered the class of compounds known as crown ethers, l i t e r a l l y thousands of applications have been developed i n which t h e i r a b i l i t y to complex metal ions, solvate inorganic and organic salts i n polar and non-polar solvents and f a c i l i t a t e anionic reactions have been e x p l o i t e d . The compounds are c y c l i c polyethylene oxides. Two obstacles have prevented t h e i r wider u t i l i z a t i o n , p a r t i c u l a r l y i n commercial processes. Current synthetic methods are extremely costly. The materials have generally high levels of t o x i c i t y . Both these factors coupled with the d i f f i c u l t y i n removing the crown ethers by processes other than d i s t i l l a t i o n have hindered wider applications. A class of compounds with complexation properties r e markably s i m i l a r t o the crown ethers, i s indicated by the following general structure R R S i (OCH CH ) Ö. A s p e c i f i c example i s dimethylsila-14-crown-5.


10

1

2

,

2

2

n

The name indicates the substituents on the s i l i c o n , the number of members i n the r i n g , and the number of oxygens. This compound may be compared to 15-crown-5. Although there i s one less member i n the ring f o r the silacrown, the longer silicon-oxygen bonds r e s u l t i n an O-Si-0 unit that i s 75% of the length of an 0-CH -CH -0 u n i t . Summation of bond lengths indicate an o v e r a l l reduction i n macrocyle circumference of 4.5% when compared to 15-crown-5. This s i m p l i s t i c comparison does not take i n t o account the puckered multidentate structure the crown ethers assume i n cation complexes. Under these conditions the differences i n structure would be expected t o be further mitigated. X-ray s t r u c t u r a l analysis which would provide a more d e f i n i t i v e basis f o r comparison has not yet been performed. Although c y c l i c polyethyleneoxysilanes have been previously reported, the r i n g structures had less members and the diameters were c l e a r l y ©mailer than lithium ions. C y c l i c siloxanes have been evaluated as complexing agents. The materials are weak ionophores with s t a b i l i t y constants f a r lower than crown e t h e r s . ' Efforts to employ the c y c l i c siloxanes to f a c i l i t a t e anionic polymerizations analogous t o crown ethers have given negative r e s u l t s . * The difference i n r e a c t i v i t y has been attributed to the lower electron density 2

2

11

1 2

1 3

1

Miller; Chemically Modified Surfaces in Catalysis and Electrocatalysis ACS Symposium Series; American Chemical Society: Washington, DC, 1982.

17.

ARKLES E T A L .

283

SUacrOWTlS

of the oxygen i n siloxanes. Nevertheless, the work may be interpreted t o suggest the replacement of a single O-Si-0 u n i t for an O-CH2CH2-O unit i n a crown ether would not eliminate i t s a b i l i t y t o form cation complexes. Results and Discussion The silacrowns are readily prepared by t r a n s e s t e r i f i c a t i o n of alkoxysilanes with polyethylene glycols. A t y p i c a l reaction is R R S i (OEt) + H0(CH CH O) JL »


X

2

2

2 1

2

n

2

R R Si(OCH CH ) Ô + 2EtOH 2

2 T\

The conditions of t r a n s e s t e r i f i c a t i o n must be selected to promote c y c l i z a t i o n i n preference to polymerization. The reaction may be catalyzed by a variety of materials, including methylsulfonic acid, toluenesulfonic acid and sodium, but titanates were generally preferred. A wide range of organic groups (R*R ) can be readily substituted to a l t e r the s o l u b i l i t y , phase p a r t i t i o n and r e a c t i v i t y of the silacrowns. The reactants are combined and approximately 80-95% of the alcohol i s slowly d i s t i l l e d from the reaction mixture. I f the silacrown being prepared contains a moiety which does not have great thermal s t a b i l i t y , such as a v i n y l group, i t i s useful t o add a higher b o i l i n g solvent such as toluene. The product i s removed from the reaction mixture by d i s t i l l a t i o n . I t appears that there i s some molecular rearrangement during the course of d i s t i l l a t i o n i n the presence of t r a n s e s t e r i f i c a t i o n catalysts that results i n the p r e f e r e n t i a l removal of the more v o l a t i l e s i l a crowns from the reaction mixture. The d i r e c t interaction of chloro, amino, and acyloxsilanes with polyethylene glycols can also lead to the desired products but i n s i g n i f i c a n t l y lower y i e l d . The silacrowns are generally c o l o r l e s s , odorless, l i q u i d s of moderate v i s c o s i t y . Sila-14-crown-5, sila-17-crown-6 and sila-20-crown-7 structures have been prepared. Substituents on the s i l i c o n include methyl, v i n y l , phenyl and methoxy groups. The compounds are tabulated below: 2

Compound

M.W.

b.p.

dimethylsila-8-crown-3* dimethylsila-ll-crown-4* dimethylsila-14-crown-5 dime thyIs ila-17-crown-6 dimethylsila-20-crown-7 vinylmethylsila-14-crown-5 vinylmethyIs ila-17-crown-6 methoxymethylsila-17-crown-6 phenylmethylsila-14-crown-5 •reported i n reference 11

162.3 206.3 250.4 294.4 338.5 252.4 306.4 310.4 312.5

90°/50 96°/9 125-130V0.5 168-170°/0.3 240-244°/0.2 129-131O/0.5 169-172°/0.3 170-173V0.3 180-185°/0.1-0.15



284


S t a b i l i t y and m e t a l i o n s a l t s o l u b i l i t i e s o f t h e s i l a c r o w n s h a v e n o t b e e n q u a n t i t a t i v e l y e v a l u a t e d . The s i l a - 1 7 crown-6 m a t e r i a l s o f f e r s i m p l e q u a l i t a t i v e e v i d e n c e o f complex f o r m a t i o n . P o t a s s i u m permanganate i s mixed w i t h c h l o r o b e n z e n e . The s a l t r a p i d l y s e t t l e s and no c o l o r a t i o n o f t h e c h l o r o b e n z e n e i s o b s e r v e d . The a d d i t i o n o f 1-2% o f t h e s i l a c r o w n produces t h e c h a r a c t e r i s t i c deep p u r p l e c o l o r o f s o l v a t e d p o t a s s i u m permanganate. A f t e r 1 hour v i n y l s i l a c r o w n s o l u t i o n s t u r n b r o w n and a f i n e p e r c i p i t a t e i s o b s e r v e d , p r e s u m b l y due t o s i l a c r o w n p r o m o t e d o x i d a t i o n o f i t s own v i n y l group. The p h a s e t r a n s f e r c a t a l y t i c p r o p e r t i e s o f t h e s i l a c r o w n s w e r e i n v e s t i g a t e d i n a number o f s y s t e m s . The s u b s t i t u t i o n r e a c t i o n o f c y a n i d e w i t h b e n z y l b r o m i d e ( T a b l e 1) was e v a l u a t e d w i t h and w i t h o u t s i l a c r o w n p r o m o t e d c a t a l y s i s and compared w i t h 18-crown-6 and d e c a m e t h y l c y c l o p e n t a s i l o x a n e (D$). R e a c t i o n c o n d i t i o n s and t i m e s w e r e n o t o p t i m i z e d . The c a t a l y t i c a c t i v i t y o f t h e s i l a - 1 7 - c r o w n - 6 a p p e a r e d t o be e q u i v a l e n t t o 18-crown-6. D o d e c a m e t h y l c y c l o p e n t a s i l o x a n e d i d not demonstrate c a t a l y t i c a c t i v i t y . The s p e c i f i c i t y o f t h e s i l a - 1 4 - c r o w n - 5 f o r s o d i u m i o n s and n o t p o t a s s i u m i o n s p r o v i d e s e v i d e n c e f o r complex f o r m a t i o n analogous t o t h e crown e t h e r s . In order t o survey anion a c t i v a t i o n , s u b s t i t u t i o n r e a c t i o n s o f h a l o g e n s , p s e u d o h a l o g e n s and o r g a n i c a n i o n s w e r e e v a l u a t e d u n d e r m i l d c o n d i t i o n s . The m a j o r i t y o f t h e r e a c t i o n s w e r e r u n by s i m p l y m i x i n g a t w i c e m o l a r e x c e s s o f t h e s a l t w i t h t h e s u b s t r a t e i n a c e t o n i t r i l e c o n t a i n i n g 0.1-0.2M s i l a c r o w n and a g i t a t i n g o v e r n i g h t . D i s p l a c e m e n t s b y c y a n i d e a c e t a t e and i o d i d e p r o c e e d s m o o t h l y . Higher temperatures are required for f l u o r i d e . The r e s u l t s a r e s u m m a r i z e d i n T a b l e I I . The s o l i d / l i q u i d p h a s e t r a n s f e r a n a l y s i s o f p o t a s s i u m cyanide i n a s e r i e s of s u b s t i t u t i o n reactions are indicated i n Table I I I . A g a i n , t h e r e a c t i v i t y o f t h e s i l a c r o w n s appear comparable t o crown e t h e r s . The f i r s t s i l a c r o w n s p r e p a r e d f o r i m m o b i l i z a t i o n c o n t a i n e d v i n y l f u n c t i o n a l i t y . A t t e m p t s w e r e made t o i n t r o d u c e s u p p o r t r e a c t i v i t y b y h y d r o s i l y l a t i n g t h e compounds w i t h t r i c h l o r o s i l a n e and m e t h y l d i m e t h o x y s i l a n e . A l t h o u g h t h e h y d r o s i l y l a t i o n s p r o c e e d s m o o t h l y , w i t h i n 1-15 m i n u t i e s t h e m a t e r i a l s u n d e r w e n t r a p i d secondary r e a c t i o n s t o form g l a s s y s o l i d s o r v i s c o u s liquids. S i l a c r o w n s w h i c h may be r e a d i l y i m m o b i l i z e d on s i l i c e o u s supports are the methoxysilacrowns. L i k e o t h e r members o f t h e s e r i e s t h e compounds a r e p r e p a r e d by t r a n s e s t e r i f i c a t i o n . In t h i s case the s t a r t i n g m a t e r i a l s are t r i m e t h o x y s i l a n e s . The m e t h o x y s i l a c r o w n s behave s i m i l a r l y t o t h e o t h e r s i l a c r o w n s i n s o l i d / l i q u i d phase t r a n s f e r c a t a l y s i s . The c a t a l y t i c p r o p e r t i e s o f t h e s e compounds w e r e t r a n s l a t e d t o s o l i d s u p p o r t s b y



Values

1 0

* *Decamethylcyclopentasiloxane

•Literature

R e a c t i o n s a t room t e m p e r a t u r e i n a c e t o n i t r i l e

KCN

Solid/Liquid

KCN

Solid/Liquid KCN

KCN

Liquid/Liquid

NaCN

KCN

Liquid/Liquid

Solid/Liquid

NaCN

Solid/Liquid

Solid/Liquid

KCN KCN

Solid/Liquid

REACTANTS

Solid/Liquid

CONDITIONS

5

14-5

14-5

D **

18-6*

17-6

17-6

CATALYST

4

16

16

6

16

16

4

48

4

TIME

REACTIONS OP MCN WITH BENZYL BROMIDE

TABLE I


3%

100%

20%

100%

100%

100%

0%

54%

0%

YIELD

g

00

CA

Miller; Chemically Modified Surfaces in Catalysis and Electrocatalysis ACS Symposium Series; American Chemical Society: Washington, DC, 1982. Benzyl Acetate Benzyl F l u o r i d e B e n z y l F l o u r i d e a t r e f l u x 48 h o u r s

KOAc

KF

KF

i n a c e t o n i t r i l e w i t h 0.13M s i l a c r o w n

Benzyl Cyanide

KCN

R e a c t i o n a f t e r 16 h o u r s a t a m b i e n t t e m p e r a t u r e

PRODUCT

REACTANT

REACTIONS OF BENZYL BROMIDE + KX

SILA-17-CR0WN-6 CATALYZED

TABLE I I


g

55%

w

Î

1

w Ö

&

r

P

0

5%

100%

100%

YIELD

oo ON


25%

16 48

14--5

10

29%

16

17--6

Benzyl Chloride

75 1 16 16

18--6* 17--6

—

Benzyl Chloride

Benzyl Chloride

A l l y l Bromide

A l l y l Bromide

** mixtures of a l l y l cyanide and crotononitrile

Reactions at room temperature i n a c e t o n i t r i l e * Literature V a l u e

Benzyl Chloride

— — -*

A l l y l Bromide

16

17--6

Benzyl Bromide

0%

74%

1

99%

0%

100%

100%

100%

40 at reflux

18--6*

YIELD 63%

Hexyl Bromide

TIME 48

CATALYST 17--6

REACTANT Octyl Bromide

CATALYSIS OF POTASSIUM CYANIDE SUBSTITUTIONS

SILACROWN SOLID/LIQUID PHASE TRANSFER

TABLE I I I


288


i n c o r p o r a t i n g them i n t o a r e f l u x i n g m i x t u r e o f t o l u e n e and c o n t r o l l e d p o r e g l a s s . The i m m o b i l i z e d s i l a c r o w n may be d e p i c t e d :


">< CH

3

*) O

0

W The i m m o b i l i z e d s i l a c r o w n was added t o a t w o p h a s e m i x t u r e c o n t a i n i n g c o n c e n t r a t e d aqueous p o t a s s i u m c y a n i d e a n d s u b s t r a t e d i s s o l v e d i n a c e t o n i t r i l e . The m i x t u r e was s t i r r e d a t 6 0 0 1000 rpm. R e s u l t s a r e shown i n T a b l e I V . The i m m o b i l i z e d s i l a crown c a t a l y z e d c y a n i d e d i s p l a c e m e n t r e a c t i o n s i n t h e t h r e e c a s e s . The c o n v e r s i o n o f b e n z y l c h l o r i d e t o b e n z y l c y a n i d e p r o c e e d e d t o 100% c o n v e r s i o n , s i m i l a r t o t h e s o l u b l e s i l a c r o w n . The c o n v e r s i o n o f b e n z y l c h l o r i d e t o b e n z y l c y a n i d e p r o c e e d e d f u r t h e r than t h e s o l u b l e s i l a c r o w n . There i s i n s u f f i c i e n t data t o d e t e r m i n e w h e t h e r t h i s i s a g e n e r a l phenomenon. I t h a s been p o i n t e d o u t by o t h e r w o r k e r s t h a t s i l i c a p r o v i d e s an a d s o r p t i v e s u r f a c e t h a t can p r o v i d e a s s i s t a n c e i n phase t r a n s fer. The r e a c t i o n o f p o t a s s i u m c y a n i d e w i t h a l l y l b r o m i d e u n d e r l i q u i d / l i q u i d phase t r a n s f e r c o n d i t i o n s produced a mixture o f a l l y l c y a n i d e and c r o t o n o n i t r i l e . T h i s may b e c o m p a r e d t o t h e c a t a y s i s e x h i b i t e d b y a n o t h e r new p h a s e t r a n s f e r c a t a l y s t , immobilized t r i m e t h o x y s i l y l o c t y l t r i b u t y l a m m o n i u m bromide, which produced o n l y a l l y l cyanide. While t h i s i n i t i a l r e p o r t c l e a r l y i n d i c a t e s t h e phase t r a n s f e r c a t a l y t i c p r o p e r t i e s o f the silacrowns i n both s o l u b l e and i m m o b i l i z e d f o r m s , much i n f o r m a t i o n i s r e q u i r e d t o d e f i n e t h e i r c a t a l y t i c parameters and s y n t h e t i c l i m i t a t i o n s . C u r r e n t i n f o r m a t i o n r e g a r d i n g optimum c o n c e n t r a t i o n s , t e m p e r a t u r e s and t i m e s f o r c o n v e r s i o n s , d e t e r m i n a t i o n o f s t a b i l i t y c o n s t a n t s and s t r u c t u r a l c o n f o r m a t i o n i s i n c o m p l e t e . Long term h y d r o l y t i c s t a b i l i t y i n p a r t i c u l a r , under b a s i c c o n d i t i o n s may b e a s e r i o u s l i m i t i n g f a c t o r . 7

Experimental S i l a n e i n t e r m e d i a t e s were o b t a i n e d from P e t r a r c h Systems Fine Chemicals D i v i s i o n . P e n t a e t h y l e n e g l y c o l was o b t a i n e d from F a i r f i e l d . P o r o u s g l a s s was o b t a i n e d f r o m E l e c t r o n u c l e o n i c s . Vinylmethylsila-14-Crown-5. A 250ml s i n g l e n e c k f l a s k e q u i p p e d w i t h a m a g n e t i c s t i r r e r a n d h e a t i n g m a n t l e was c h a r g e d w i t h 0.5mole (93ml) o f v i n y l m e t h y l d i e t h o x y s i l a n e , 0.5mole(86ml) o f t e t r a e t h y l e n e g l y c o l a n d 0.5ml o f t e t r a b u t y l t i t a n a t e . The


Miller; Chemically Modified Surfaces in Catalysis and Electrocatalysis ACS Symposium Series; American Chemical Society: Washington, DC, 1982. 16 25 16

a l l y l bromide(0%) b e n z y l b r o m i d e (0%) benzyl chloride(3%)

(S) - s i l a - d 7 - 6

(§)-sila-17-6

3

16

8

a l l y l b r o m i d e (55%)

2

(§)- i n d i c a t e s s u p p o r t b o u n d

sila-17-6

(CH ) N^Bu Br

(§)-

TIME

REACTANT

CATALYST

cyanide

cyanide cyanide

benzyl benzyl

a l l y l cyanide c rotononit r i le

allyl

PRODUCT

PROMOTED CYANIDE SUBSTITUTION

IMMOBILIZED PHASE TRANSFER CATALYST

TABLE I V


290


m i x t u r e was s t i r r e d a t 50-60° f o r 16 h o u r s w i t h a c o l d f i n g e r d i s t i l l a t i o n head i n p l a c e . The p o t t e m p e r a t u r e was i n c r e a s e d t o 85-100° and a b o u t 50ml o f e t h a n o l was r e m o v e d . The m i x t u r e was t h e n d i s t i l l e d u n d e r vacuum. T h e f r a c t i o n b o i l i n g a t 129131° a t 0.5mm was c o l l e c t e d . A p p r o x i m a t e l y 62g o f v i n y l m e t h y l s i l a - 1 4 - c r o w n - 5 was i s o l a t e d . T h e compound was i d e n t i f i e d b y i n f r a r e d and o r g a n i c mass s p e c t r o s c o p y . As expected the compound d i d n o t e x h i b i t a m o l e c u l a r i o n , b u t e x h i b i t e d (M-CH )+ a t 247 a n d (M-CH=CH )+ a t 235. 3


2

Vinylmethylsila-17-Crown-6. U n d e r t h e same c o n d i t i o n s d e s c r i b e d a b o v e 37.4ml o f v i n y I m e t h y l d i e t h o x y s i l a n e , 4 6 . 6 g o f p e n t a e t h y l e n e g l y c o l , 0.2ml o f t e t r a i s o p r o p y l t i t a n a t e a n d 25ml o f t o l u e n e w e r e c h a r g e d i n t o a 250ml f l a s k . A p p r o x i m a t e l y 20ml o f e t h a n o l was removed a t a t m o s p h e r i c p r e s s u r e . T h e p r o d u c t f r a c t i o n was c o l l e c t e d a t 169-172° a t 0.3mm. T h e y i e l d w a s 36g. T h e a n a l y s i s was p e r f o r m e d a s a b o v e . D i m e t h y l s i l a - 1 7 - C r o w n - 6 and Dimethylsila-20-Crown-7. U n d e r c o n d i t i o n s s i m i l a r t o t h o s e d e s c r i b e d i n example""! 148.3g o f d i m e t h y l d i i n e t h o x y s i l a n e was c o m b i n e d w i t h 300g o f a m i x t u r e o f p o l y e t h y l e n e g l y c o l s w i t h a n a v e r a g e m o l e c u l a r w e i g h t o f 300. 230g o f d i m e t h y l s i l a - 1 7 - c r o w n - 6 , b.p. 169-170° a t 0.3mm and 45g o f d i m e t h y l s i l a - 2 0 - c r o w n - 7 , b . p . , 240-244° a t , 0.2mm w e r e obtained. The r e m a i n i n g s i l a c r o w n s w e r e p r e p a r e d s i m i l a r l y . I m m o b i l i z a t i o n o f Methoxymethylsila-17-Crown-6 2

C o n t r o l l e d p o r e g l a s s (80-120mesh, 226A, 99m /g) was t r e a t e d w i t h 10-15% H C l o v e r n i g h t t o i n d u c e s i l a n o l f o r m a t i o n , washed w i t h w a t e r and d r i e d f r e e o f b u l k w a t e r . A s i n g l e neck f l a s h was c h a r g e d w i t h 50ml o f a 2% s o l u t i o n o f m e t h o x y m e t h y l s i l a - 1 7 - c r o w n - 6 a n d l O g o f p o r o u s g l a s s . The m i x t u r e was r e f l u x e d o v e r n i g h t . T h e t r e a t e d b e a d s w e r e washed w i t h t o l u e n e and d r i e d . 8-Bromooctyltrimethoxysilane. A 3 neck 1 l i t e r f l a s k e q u i p p e d w i t h m a g n e t i c s t i r r e r , a d d i t i o n f u n n e l and c o n d e n s o r was c h a r g e d w i t h 4 0 0 m l o f t r i m e t h y l o r t h o f o r m a t e and warmed t o 30-35°. O v e r t h e c o u r s e o f t h r e e h o u r s 327g o f 8 - b r o m o o c t y l t r i c h l o r o s i l a n e was a d d e d . T h e m i x t u r e was d i s t i l l e d . The f r a c t i o n b o i l i n g a t 127-130°/2mm was i d e n t i f i e d a s 8 - b r o m o o c t y l t r i m e t h o x y s i l a n e , 93% y i e l d . N- ( 8 - t r i m e t h o x y s i l y l o c t y l ) t r i b u t y lammonium B r o m i d e * Bromoo c t y l t r i m e t h o x y s i l a n e , 31.3g(53.1ml) o f m e t h a n o l a n d 23.8ml. o f t r i b u t y l a m i n e w e r e c o m b i n e d i n a 250ml s i n g l e n e c k f l a s k and r e f l u x e d f o r 16 h o u r s . T h e p r o d u c t was r e t a i n e d i n 50% m e t h a n o l s o l u t i o n .


17.

ARKLES E T A L .

Silacrowns

291

Immobilized N ( 8 - t r imethoxy s i l y l o c t y 1 ) tributylammonium Bromide. 50mls o f a 5% s o l u t i o n o f t h e name compound was p l a c e d i n a 150ml b e a k e r . The s o l u t i o n was warmed t o 35° a n d l O g o f t h e p r e t r e a t e d p o r o u s g l a s s d e s c r i b e d above was a d d e d . T h e m i x t u r e was s t i r r e d m a n u a l l y . The s u p e r n a t a n t was d e c a n t e d . The p o r o u s g l a s s was w a s h e d t w i c e w i t h m e t h a n o l a n d d r i e d o v e r n i g h t a t 50-60°.


S o l i d / L i q u i d Phase T r a n s f e r

Experiments

The g e n e r a l p r o c e d u r e f o r t h e e x p e r i m e n t s was t o c o m b i n e 0.05M o f o r g a n i c r e a c t a n t w i t h 0.10M o f i n o r g a n i c r e a c t a n t ( n e a t o r s a t u r a t e d a q u e o u s s o l u t i o n ) , 25ml o f a c e t o n i t r i l e a n d lml of silacrown. F o r c o m p a r a t i v e p u r p o s e s c o n t r o l and l i t e r a t u r e e x a m p l e s o f 18-crown-6 a r e r e p o r t e d , unless otherw i s e noted t h e r e a c t i o n s were r u n a t ambient temperature. P r o d u c t c o n v e r s i o n was d e t e r m i n e d b y g a s c h r o m a t o g r a p h y . L i q u i d / L i q u i d Phase T r a n s f e r

Experiments

A c o n c e n t r a t e d aqueous s o l u t i o n o f p o t a s s i u m c y a n i d e was p r e p a r e d c o n t a i n i n g l g o f KCN i n 2ml o f s o l u t i o n . 0.05M o f o r g a n i c r e a c t a n t was c o m b i n e d w i t h 0.1M o f aqueous KCN a n d 2 g o f s i l a c r o w n t r e a t e d p o r o u s g l a s s . The r e a c t i o n m i x t u r e s w e r e s t i r r e d a t 600-1000 rpm w i t h a m a g n e t i c s t i r r e r . Product c o n v e r s i o n was d e t e r m i n e d b y g a s c h r o m a t o g r a p h y . Conclusions A new c l a s s o f compounds, m a c r o c y c l i c p o l y e t h y l e n o x y s i l a n e s , c a l l e d s i l a c r o w n s have been p r e p a r e d which demonstrate phase t r a n s f e r c a t a l y t i c p r o p e r t i e s . An a l k o x y f u n c t i o n a l s i l a c r o w n has been i m m o b i l i z e d i n a s i n g l e - s t e p r e a c t i o n on a s i l i c e o u s support. The i m m o b i l i z e d s i l a c r o w n a l s o d e m o n s t r a t e s phase t r a n s f e r c a t a l y t i c p r o p e r t i e s . A f u n c t i o n a l i z e d onium phase t r a n s f e r c a t a l y s t was a l s o p r e p a r e d t h a t r e a c t s d i r e c t l y w i t h a s i l i c e o u s support and i s c a t a l y t i c a l l y a c t i v e .


292



LITERATURE CITED 1. S. L. Regen, J. Am. Chem. Soc. 97, 5695 (1975) 2. S. L. Regen, J. Am. Chem. Soc. 98, 6720 (1976) 3. S. L. Regen, J. Org. Chem. 42, 875 (1977) 4. M. Tomoi, W. Ford, J. Am. Chem. Soc. 103, 3821 and 3829 (1981) 5. M. Cinquini, S. Collons, H. Molinari, F. Montanari and F. Tundo, J. Chem. Soc. Commun. 394, (1976) 6. M. Tomoi, O. Abe, M. Ikeda, K. Kihara, H. Kakiuchi, Tetraedron Lett., 3031 (1978) 7. P. Tundo, P. Ventarello, J. Am. Chem. Soc., 101, 5505 (1979) 8. T. Waddell, D. Leyden, D. Hercules i n "Silylated Surfaces" ed. by D. Leyden and W. Collins, Gordon and Breach, N.Y. (1980) 9. T. Waddell, D. Leyden, J. Org. Chem. 46, 2105 (1981) 10. R. Izatt, J. Christensen "Synthetic Multidentate Macrocylic Compounds" Academic Press, N.Y. (1978) 11. R. Krieble, C. Burkhard, J. Am. Chem. Soc. 69, 2689 (1947) 12. C. D. Olliff, G. Pickering, K. Rutt, J. Inorg. Nucl. Chem. 42, 288 (1980) 13. C. Olliff, G. Pickering, K. Rutt, J. Inorg. Nucl. Chem. 42, 1201 (1980) 14. Yu Yuzhelevskii, V. Pchelintsev, N. Fedoseeva, Vysokomol Soedin Ser. B 18(II) 873, (1975) Chem. Ab. 86: 73181v RECEIVED November 17, 1981.


Silacrowns, a New Class of Immobilizable Phase Transfer Catalysts

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