The Hg sensitized vapor phase photolysis of cyclic anhydrides

TetrahedronLettersNo.50, PP. 4549-4552,1%.

THE Hg s2NsITIm

VApaR HiAm

PergamonPress. Printed in Great Britain.

FHuromsIs

OF CYCUC ANHYDRIDES

I. S. KniU* and D. R. Arnold Union Carbide Research Institute,P. 0. Box ~78, Tarrytown,N. Y. 10591 (Beceiredin usli22 hgust

1969; rbceived in 1H tar mrblioafi)n23 Septabor 1969)

We have reported the mercury sensitizedvapor phase photolysisof cyclic la&ones and butenolidesleading to the extrusionof carbon dioxide and formationof cyclic hydro1 carbons.

The course of this reaction is formallyanslogousto the well studied extrusion

2 of carbon monoxide fran cyclic ketones.

Tbis study has now been extendedto cyclic an-

hydrides,where both decarbonylationati decarboxylationoccur.3i4

Table

*

Anbydride

Percent Conversion

Products (PercentYields)

succinic

33.0

c%+=~

gluteric

44.0

CR2=CH2 (4.7); Hcdi b

adipic

(15.4);w.wx

(38.2) (23.5);v(53.8);

(0.4);CIQ=C=O (Trace)

CIQ=CH2 (23.3); I-E&H (54.3);V(Tmce);

30.0

A c=2q

(l.9);0( 5.0); CH2=C=0 (Trace) (7.5); H(;~CH (30.0); J

cis-cyclobutanenarboxylic

20.0

maleic

20.0

HCnCH (83.1)

dimetlqlmaleic

26.0

cH3CrCCH3

(3.8);

@I (7.5)

(33.0); CH2=CH2 (1.7);HCaCH

(1.1);CH3CxCH (0.7);[(0.6); HC&H2CH3

*

Sane polymer formed on the walls of the irradiationvessel

'Union Carbide CorporationPost-doctoralFellow, 1968-69.

4349

(0.6);CH2=C=CHCH3(0.6)

in all cases.

No.50

4350 The results sxe sununarized in the Table. All photolyseswere carried out on a one grsm scale; however, the apparatusand flow techniquesre such that larger smounts of

the anhydridecould easily have been used. The startingmaterialswere availableccnnmercially, and were purifiedby recrystallization or cohrmn chrcauatcgrapby when necessary. Gaseous photoproductswere identifiedby standardanalyticalproceduresand cunpsxedwith authentic materials. Wrcent yield6 were determinedby rmr utilizingau internal standard. The major bydrocarbbnproducts can be accountedfor by the extrusionof carbon dioxide and carbon monoxide $th foormation of the diradicalII, followedby bonding, frwentation, or wdrogen migration 5 Compoundsresultingfran secondaryreactionsof the

II initisJ_ products are also formed. secon&uy reactionmay occur either before vibrational deactivation,or upon furtherppotolysis (e.g.,acetylenefrun succinicanhydride;1,3butsdienefrau -cis-cyclobutanedicarbowlic anhydride). The formationof ketene fran glutaric and adipic -ides

was unexpected,since

it cannotbe accountedfor by the above mechanism. Additionalproof for its presence in addition to the ir, was formationof acetanilide(ir,mass spectnrm,mp) upon .%Mition of aniline to the gaseous photoproducts. One possiblemechanism for the formationof ketene is frsg6 mentation of the acyl &radical (III),which would result frcaninitial acyl-oxygencleavsge. diradicalformed as an inter-

This fragmentationis believed to occur with the l,h-acyl a&l

7-9 However, dirsdicalIII is a proposed mediate in the photolysisof cyclobutanone.

,*

co + /-

z3> vapor v

K.

n

l-

+ 2CH2=CH2

No.50

4351

2,lOJ.l intermediatein the vapor phase photolysisof cyclopentanone, where ketene has not been observedemong the products. Attempts at characterizingproductswhich might have arisen via a stepwiseextrur I2 sion process have not been successful. This is not unexpected,however, since decarbonylation, decarboxylation,or cleavegeof the intermediateacyl or acyloxy diradicalshould be rapid relative to closure.3'13-15 The mercury sensitizedvapor phase photolysisof cyclic anhydridesprovides a novel exsmple of extrusionreactions. The simplicityof the apparatusand technique,snd the ready availabilityof anbydrides,make this a premising syntheticmethod for cyclic t@rocarbons. References

(1) I. S. Erull.and D. R. Arnold, TetrahedronLetters,1247 (1969). W. A. Noyes, Jr., G. S. Rsnuuond, and (2) R. Srinivasanin "Advancesin Photochemistry," J. N. Pitts, Jr., Editors, Vol. 1, W. J. Wiley and Sons, Inc., New York, N. Y., 1963, PP 83-113. (3) P. Ausloos, Can J. Chem., $4, 1709 (1956). The direct vapor phase photolysisof acyclic anhydrideshas been shown to involve two primary processes: a) cleavageto an acyloxy and acyl radical; and b) frwentation to a ketene and an acid via a cyclic six-membered transitionstate. The latter pathwq is stericallyprohibitedin the cyclic anbydrides reportedhere. J. Wiley snd Sons, Inc., New York, (4) J. G. Calvert and J. N. Pitts, Jr., "Photochemistry," N. Y., 1966, PP 433-434. (5) For a general review of this area, see: B. P. Stark and A. J. Duke, "ExtrusionReactions," PergemonPress, London,England, 1967, Chaps. l-4. (6) The greater stabilityof the acetyl over acetoxy radical when generatedat low temperatures by the vapor phase photolysisof acetic anhydrideis consistentwith formationof III.3 (7) IL 0. Dens&lag and E. E. C. Lee, J. Am. Chem. Sot., 3, 4795 (1967). (8) E. w. S&lag, et al., E,

3,

5098 (1967).

(9) T. I-LMcGee, J. whys. Chen., 'jz,1621 (1968).

No.50

4352 (10) H. M. Frey, Chem. and Ind., 1367 (1961). (11) H. M. Frey, w,

947 (1966).

(12) Trace smnmts of 7-butyrolactone(glutaricwdride)

and cyclopentanone(sdipic

anbydride)were detectedby vpc, however, they were not isolatedor characterized further. (13) B. Rickborn,et al., Chem. and Ind., 1951 (1964). (14) B. Rickborn,et al., J. Whys. Chem., 6&

3225 (1965),and referencestherein. The

2,6_dimetbylcyclohexanone to the -cis-issueris a minor pathway (C 5$) under vapor phase photolyticconditions. (15) J. G. Calvert s& J. N. Pitts, Jr., "Photochemistry," J. Wiley md Sons, Inc., New York, N. Y., 1966, m

3&m.