Photochemical cycloadditions of thioparabanates to olefins

TetrahedronLetters NO.

38,

PHOTOCHEMICAL

pp

3397

-

34009

CYCLOADDITIONS

OF THIOPARABANATES

TO OLEFINS

and Sonja Nieberl

Hans Gotthardt* Institut fiir Organische

PergamonPress. Printed in Great Britain.

1974.

Chemie der Universitgt Karlstrasse

Miinchen, D-8000 Miinchen 2,

23, Germany

(Receivedin IJK1 August 1974; acceptedfor publication9 AWuat 1974) Diarylthioketones 1,2 , thiophosgene3, substituted

alkenes under photochemical

some cases,

1,4-dithianes.

reduction

in ethanolic

5

methyl-2-butene banates,

conditions

However,

1, are highly reactive

react with and in

A, undergo photo-

the formation of a small amount

has also been observed

. In this communication,

4

to give thietanes

It is known that thioparabanates,

solution5.

of a thietane derivative

and thione carbonates

(3%)

in the reaction of 18 with 2-

we would like to report that thiopara-

towards electron-rich

and electron-poor

olefins,

if they are excited using light of proper wavelength. It might be mentioned phenyl-2-thioparabanate

that the uv absorption (la) -= exhibits

at 4450 a (E = 52), whereas, Consequently,

irradiation

tive excitation

spectrum

the n+n * transition

the long-wavelength

(benzene) of 1,3-diof the C=S chromophore

IT+TI * transition

of 1 using light of wavelength

lies at 3125 8.

>4000 8 allows a selec-

of 1 to the n,a* state.

c2H50-CH=CHZ +

0

P N

0

l-3= I

+hu

+

S

0

=-4000;

0

CH3 ti

n= Y

kH3

2 :

R =

C6H5

$J :

&.:

R =

CH3

2

R =

: R=

3397

C,H, CH,

/H

c\

,

=3

OC2Hs

3398

No. 38

When a degassed was irradiated derivative, methanol

benzene solution of 12 (0.014 m) and ethoxyethylene

using >4000 2 light, colourless

12, were obtained

crystals of the Spiro thietane

in 88% yield, after recrystalization

(22: mp 198.5 - 200.5O; ir, 1745 cm-'

7.1 Hz, CH3), 7.73

(t, J = 8.5 HZ, CH), 7.28

7.1 Hz, 0CH2), 5.33

(0.32 m)

from

T = 8.79

(C=O) ; nm2,

(t,

(t, J = 8.5 Hz, CH), 6.44

J = (q, J =

(mc, 2 C6H5); ms7, m/e = 354 (M+),

(t, J = 8.5 Hz, CH), 2.46

308 (M+-CH2S), 282 (M+-C4H80)). The peak at m/e, 308 strongly suggests that the ethoxy substituent

is attached at the 3-position.

The photochemical gave a mixture 1720 cm-'

reaction

of pg and 2 (65:35), in a 77% yield (C6H6), 'c = 9.19

(C=O); nmr

CH2) I 6.93

of 12 with ethoxyethylene,

(q, J = 7.2 Hz, 0CH2),

(22: mp 138 - 139O; ir, 1738,

(t, J = 7.2 Hz, CH3), 7.36

7.03, 6.79

CH) : ms, m/e = 230 (M+), 184 (M+-CH2S), 158 T = 8.62

on the other hand,

(Zs, 2 NCH3), 5.45 (M+-C4H80); 1:

,

(t, J = 7.1 Hz, CH,), 6.75, 6.44 (2s, 2 NCH3), 5.95

3.99

(s,

(t, J = 8-4

mp103-106°;

3

OCH2)

(d, J = 8.4 Hz, Hz,

nmr,

(g, J = 7.1 Hz,

=CH); ms, m/e = 184 (M+)). The formation of 1 in this reaction -

may be rationalized

in terms of the photofragmentation

of 2:.

R

'\CO

4 =

=5

R z k I-

2CH 3

C6H5 CH3

Also, it has been observed that alkenes having electron-withdrawing tuents, react with i to give thietanes. methyl acryl‘ate gave a mixture ir, 1750, 1726 cm-' OCH3) I 5.44

Thus, irradiation

of 12 in presence

of 1~ and 22 in a 45:55 ratio

(C=O); nmr, T = 7.56, 7.33

(t, J = 9.0 Hz, CH), 2.46

substiof

(Aa: _= mp 122 - 124O;

(2t, J = 9.0 Hz, CH2), 6.28

(s,

(mc, 2 C6H5); ms, m/e = 368 (M+), 322 (M+-

3399

Ho. 38

CH*S)

I

282 (M+-C4H602): 22: mp 205 - 207O; ir, 1760, 1706, 1665 cm-'

T = 6.90

(C=O); nmr,

(s, OCH3), 5.08 (s, =CH2), 2.71 - 2.36 (m, 2 C6H5); ms, m/e

Similarly,

= 322

the reaction of Lg with methyl acrylate yields a mixture

(M+)).

of &

(60%) and ZB (25%) ($g: mp 165.5 - 167O; ir, 1758, 1747, 1732 cm-' (C=O); WI

T = 7.03 (t, J = 9.4 Hz, CH), 6.71, 6.66 (2s, 2 NCH3), 6.46 (t, J = 9.4 Hz, CH), 6.30

(s, 0CH3), 5.26 (t, J = 9.4 Hz, CH); ms, m/e = 244 (M+),

198

(M+-CH2S),

158 (M+-c~H~o~); zg: mp 152 - 153O; nmr, r = 6.70, 6.41 (2s, 2 NCH3), 6.17 0CH3)r 4.82

(s, =CH); ms, m/e = 198 (M+)).

It has been reported thyl-2-butene5.

that no photocycloaddition

In contrast,

of 12 in presence

of 2-methyl-2-butene

(2s, 2 CH3), 7.04

occurs between &

and 2-me-

our findings show that the light-induced

(2: mp 256 - 257O; ir, 1740 cm-' 8.93, 8.85

(s,

reaction

yields the 1:1-adduct, 2 in a 30% yie.ld

(C=O); nmr, f = 9.08 (d, J = 7.0 Hz, CH3),

(g, J = 7.0 Hz, CH), 2.48 - 1.88 (m, 2 C6H5); ms,

m/e = 352 (M+), 292 (M+-C2H4S), 282 (M+-C5Hlo)).

c6HS

FM3

S

p.P

,CH3 C\ CH3

(CH3)*

C6H5

CH3

=6

Finally,

=7

the reaction

of LQ with tetramethylallene

under similar conditions

gave a 22% yield of z

(2: mp 207 - 208O; ir, 1740 cm-'

(s, 2 CH3), 8.36, 8.21

(2s, 2 CH3), 6.56

(C=O); nmr, r = 8.52

(s, 2 NCH3); ms, m/e = 254 (M+), 168

(M+-C4H6S), 158 (M+-C7H12)). The scope and mechanism under investigation. Acknowledgement: support.

of these photochemical

All new compounds

cycloadditions

gave satisfactory

We thank the Fondsder Chemischen

are presently

analytical

results.

Industrie for financial

No. 3s

3400

REFERENCES 1.

A.Ohno, Y.Qhnishi,

2.

H.Gotthardt,

and G.Tsuchihashi,

Chem.Ber.

IQ& -_-

2008

J.Amer.Chem.Soc.

W,

5038

(1969).

(1972); lpz, 1856 (1974), and references

cited there. Tetrahedron

Lett. 1221, 1221. -_--

3.

H.Gotthardt,

4.

H.Gotthardt

and M.Listl,

Tetrahedron

5.

T.Yonezawa,

M.Matsumoto,

Y.Matsumura,

2323

6.

and H.Kato, Bull.Chem.Soc.Jap.

22,

(1969).

If not stated otherwise, internal

7.

Lett. 1923, ---- 2849.

the nmr spectra were taken in CDC13 with TMS as

standard, on a Varian A60, spectrometer.

The mass spectra were determined 70 ev.

using a AEI MS 902, mass spectrometer

at