Tetrahedron Letters No.47, pp. 4103-4106, 1969. Pergamon Press. Printed in Great Britain.

PHOTOCHEMICAL CYCLOADDITION OF E-ACETOXYPENT-2-EN-l-ONES TO l,l-DIETHOXYETHYLENE

AND FOBMATION OF BICYCL0[2,2,1) HFZ'TANE FROM THE ADDUCT

!BtkeshI Matsumoto, Haruhlsa Shlrahama, Akltaml Ichlhara,

Shohel Kagawa and SoJIro Matsumoto

Department of Chemistry, Faculty of Science,

Hokkaldo University, Sapporo, Japan

(Received in Japan 5 July 1969; received in UK for publication 8 September 1969)

The present study of the photochemical cycloaddltlon o? enol acetates of

cyclic 1,2-dlketones to l,l-dlethoxyethylene has been InItIated with the hope of

applioatlon to the synthesis 2 of some sesquiterpenes, I.e. Illudol etc.3. There

Is little known concerning the stereoeelectIvIty and orlentatlonal mode of the

cycloaddItIon4 to dlosphenol acetates.

0

AC 9 R

9 F?=c* -lL ..$ :?b

lzto R=H 2 R”=ys 3 S

Compounds 1,2 and 1 were prepared according to the known procedures. 5 z+

Irradiation of a solution of $/in 1,1-diethoxyethylene for 3 hr with a 75 W high

pressure murcury lamp (Pyrex filter) under nitrogen led to an oily product, b.p.

114-118;/7mmHg, which, after purification by preparative gas chromatography,

gave an addition product sC14H2205,61) ~~~t1750, 1250, 1070 ~'1; r ccl4 a.78

(3H, 81, 8.70 (61i, t), 7.80 (3H, s), 6.45 (4H, q) in 64% yield. Similarly, Ir-

radiation of compound 2 gave a photoadduct 5. m/e 256 (M').$zztt 1750, 1245,

1060 crn-;~ cc14 8.80 (6H, t), 7.93 (3H, d': 6.55 (4H, q). On treatment with

sodium ethaxlde in ethanol, % was converted, after alcoholysls of the acetoxy

4103

No.47

4104

group, to a produot 6_, C12H2004, m.p. 77-77.5",L)zy 3460, 1783, 1000-1100 cm -1;

+ Cl4 8.95 (3H, s), 8 .88 (3H, t), 8.85 (3% t) in 54% yield. The high frequency7

of the carbonyl band of the product indicates that a blcyclo(2,2,1]hePtane

derivative i la produced. lhe skeletal change of k to 2 suggests that the

compound 2 has an 4 ketol moiety and the reaction could be explained in terms of

acyloin rearrangement.

Orlentatlonal mode of the photoaddition was confirmed with the derivative

10 of 4.

7 R--H 8 R=Ms

Reduction of 4 with sodium borohydride In ethanol afforded an alcohol29

3 max nu501 3450, 1725, 1060 cm -1 :7 c'=4 8.78 (3H, s), 8.74 (3H, t), 8.70 (3Hs t). neat

7.90 (3H, s), and a mi2or amount of a dlol gymax 3380, 1075 cm-1; zcc14 8'98

(3H, s), 8.85 (6~, t). me alcohol 1 was treated with mesyl chloride in pyrldine

to give a mesylate EI,JJ~E"," 1740, 1250, 1180 cm-l; T cm4 8.83 (3H, s), 8.81

(6H, t), 7.92 (3H, S), 7.00 (3H, S), 6.55 (4H, q), 4.53 (1H, t). me mesylate

was then treated with sodium ethoxlde to glve an epoxlde 9, Cl2H2003~ m/e 212

(M+);y::tt 3380, 1110, 1015 cm"; rc14 8.97 (3H, s), 8.83 (3% t), 8.80 (3H, t),

No.47 4105

6.50 (41.x, ml. The formation of the epoxlde 2 Indloater that the hydroxyl group

in compound2 Is oriented In trans to the vlclnal aoetoql group, and an alcoholate

anion (a) formed by alaoholysls of the aoetoxy group of the mewlate & attaoka

from back side of the mesyloxy group. ReauotIon of zulth lithium aluminum hydride

afforded a mono-01 012H2203w~,,

neat 3380, 1110, 1050 ~irn-~,~~~4 8.97 (3H, 8).

0.83 (31i, t), 8.80 (3H, t), 6.50 (4H, m) to which a tertiary alcohol structure l,o

was assigned, since the hydroxyl group uaa not acetylated by acetic anhydride-

pyrldlne at room temperature. This ooncluslon Is supported further by the n.m.r.

spectrum of 10. &

The Infrared spectrum of 12 In carbon tetrachlorlde (3.3~10'~ mol./l) ehoued

only an absorption band at 3630 cm" due to free hydroxyl group. Since strong

Intramolecular hydrogen bond at 3558 cm" has been detected In cyclobutane

derivative 12' and no hydrogen bond In compound lz,9 orientational mode for the

photoadduct must be described as 4 and another possible orlentatlon 12 la

excluded.

;K@ ,s Eq?Q

B g B

The e-configuration of the photoaaduct 2 was deduced by the n.m.r. spectra

In which the signals (8.78 in f and 1, 8.83 in 2) due to angular methyl group

In acetoxy compounds were shifted by the replacement of acetyl group through

hydrogen to higher field (8.97 In 2 and 12, 8.98 In 1211'.

The enol acetate 3 of cyclohexanedlone was found to be Inoperative In the d

photoaddition reaction under the standard reaction conditions for 1 and 2. The

reason Is not clear at present.

REFERENCES

1. Presented at the 22nd annual meeting of the Chemical Society of Japan,

Tokyo, April 1969.

4106 No.47

2. S. Kagaua, S. Natsumoto, H. Nlshlda, S. Yu, J. Morlta, A. Ichlhara,

H. Shlrahama and T. Matsumoto, Tetrahedron Letters, submitted for publication.

3. T. C. McMorrIs, M. S. B. NaIr, M. Anchel, J. Am. Chem. Sot., 92, 4562 (1967).

4. An example of Intramolecular photocycloaddltlon of dlketone enol ether

(a tropolone derivative) has been known; W. G. Dauben, K. Koch and W. E. 'Ihiessen,

J. Am. Chem. Sot., ii, 6087 (1959).

5. G. Heese and K. W. F. mckmann, &., 361, 37 (1949); W. Dieckmann, &r., -I

31, 3201 (1902); 0. Wallach, a., 232, 173 (1924).

6. Satisfactory analytical data were obtained for all the new compounds Indicated

by molecular formulae.

7. P. G. Gassman, P. G. Pape, Tetrahedron Letters, 9 (1963).

8. R. Crlegee and K. Noll, &., &?2, 1 (1959).

9. C. Beard and A. Burger, e., nj, 2535 (1962).

10. It is known that Irradiation of 2-cyclopentenone In 1,1-dlmethoxyethylene

gave a cls-photoadduct as a single addition product; E. J. Corey, J. D. BBss, -

A. Lemahlen and R. B. Mltra, J. Am. Chem. Sot., E& 5570 (1964).