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Deketalization Induced byPhenyl Dichlorophosphate andSodium IodideHsing-Jang Liu a & Shu-Yuan Yu aa Department of Chemistry , The University ofAlberta Edmonton , Alberta, Canada , T6G 2G2Published online: 05 Dec 2006.

To cite this article: Hsing-Jang Liu & Shu-Yuan Yu (1986) Deketalization Inducedby Phenyl Dichlorophosphate and Sodium Iodide, Synthetic Communications: AnInternational Journal for Rapid Communication of Synthetic Organic Chemistry, 16:11,1357-1361, DOI: 10.1080/00397918608056383

To link to this article: http://dx.doi.org/10.1080/00397918608056383

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SYNTHETIC COMMUNICATIONS, 16(11), 1357-1361 (1986)

DEKETALIZATION INDUCED BY PHENYL DICHLOROPHOSPHATE AND SODIUM IODIDE

Hsing-Jang Liu* and Shu-Yuan Yu

Department of Chemistry, The University of Alberta Edmonton, Alberta, Canada T6G 2G2

Abstract: Treatment of ketals with phenyl dichlorophosphate and sodium iodide in refluxing benzene gave rise to ketones.

Ketal is the most extensively used functionality

for the protection of ketone carbonyl. The removal of

this protecting group is normally carried out under

acidic conditions.'

synthetic utility, alternative methods involving non-

acidic reagents are rather few in number.2

communication, we wish to report a new procedure which

effects deketalization under virtually neutral

In spite of their apparent

In this

conditions.

During the course of our recent studies on the

transformation of @ -diketones to B-halo-a ,@-unsaturated

ketonesI3I4 it was observed that, on exposure to phenyl

dichlorophosphate and sodium iodide, tetrahydrofuran

* To whom correspondence should be addressed.

1357

Copyright 0 1986 by Marcel Dekker, Inc. 0039-791 1/86/1611-1357$3.50/0

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1358 LIU AND YU

underwent facile ring cleavage to give lr4-diiodo-

butane5 presumably via the route shown in Scheme 1. An

extrapolation of this unexpected finding suggested that

the combination of phenyl dichlorophosphate and sodium

iodide could in principle, induce deketalization on the

basis of the hypothetical pathway outlined in Scheme 2.

Scheme 1

PhOPOC12 NaI

t

NaI WH2)41 -

0 @-V-OPh

X

(X=CI or I)

h a 1

0 II I

X

I ( CH ,),O-P-O P h

Scheme 2

0 II I

X-P-OPh

0 7 .)( 3 ~ 2 ) n R O

(X=CI or I)

9 NaI 9 a 52 R! R! X

C=O - C=OCH2(CH2),CH2O-:-OPh

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DEKETALIZATION 1359

In accordance with the expection, when 2,2-

dibutyl-1,3-dioxolane was treated with phenyl dichloro-

phosphate (1.2 equiv.) and sodium iodide (3 equiv.) in

refluxing benzene for 12 h, 5-nonanone was obtained in

90% yield, after the usual work-up under basic condi-

tions (aqueous sodium hydroxide with dichloromethane

extraction) and distillation. The reaction is

apparently general. Table 1 summarizes the results

obtained for a number of ketals examined including both

1 , 3-dioxolane (Entries 1-6) and 1 , 3-dioxane derivatives (Entries 7 and 8). The described reaction conditions

were shown to be generally effective for both of these

types of commonly used cyclic ketal protecting

groups.6

however observed, with the six-membered ones reacting

at a considerably slower pace (cf. Entries 4 and 7 )

apparently due to the greater stability.

A marked difference in reaction rate was

Under similar conditions, neither phenyl dichloro-

phosphate alone nor its combination with lithium

chloride was found to effect deketalization even over

an extended period of reaction time. Hence, it is most

likely that either phenyl chloroiodophosphate

(PhOPOClI) or the corresponding diiodo compound

(PhOPO12) generated in situ served as the activating

agent .

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1360 LIU AND YU

Table 1. Deketalization with Phenyl Dlchlorophosphate and Sodium Iodide

Entry Keial Time (h)' Product % Yleldb

6

n 12

n fl 20

16 n

n 16

20

36 n

24

A 90

A 100

$ 73

96

93

53

'All reactions were carried out in refluxing benzene using 1.2 equiv. of

bAll yields given are for isolated products and have not been optimized

PhOPOCI, and 3 equiv. of NaI

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DEKETALIZATION 1361

Acknowledqment : We a re g r a t e f u l to t h e Natura l

S c i e n c e s a n d E n g i n e e r i n g R e s e a r c h C o u n c i l o f C a n a d a a n d

t h e U n i v e r s i t y o f A l b e r t a f o r f i n a n c i a l s u p p o r t .

R e f e r e n c e s and Notes

1. G r e e n e , T.W., " P r o t e c t i v e G r o u p s i n O r g a n i c

S y n t h e s i s , " J o h n W i l e y a n d S o n s , New York , 1981.

2. J u n g , M.E. , A n d r u s , W.A., a n d O r n s t e i n , P .L . ,

T e t r a h e d r o n L e t t . , 1977, 4175.

3 . L i u , H . J . a n d L l i n a s - B r u n e t , M., Can. J. Chem.,

1 9 8 4 , 62, 1 7 4 7 .

4. L i u , H . J . , Lamoureux, G . V . , and L l i n a s - B r u n e t , M.:

Can. J. Chem., i n press.

5. L i u , H . J . , Shewchuk, L.M., a n d L l i n a s - B r u n e t , M.,

u n p u b l i s h e d r e s u l t s .

6. I o d o t r i m e t h y l s i l a n e h a s b e e n f o u n d n o t t o be

h i g h l y e f f e c t i v e f o r t h e removal of t h e c y c l i c

k e t a l s . *

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