Tetrahedron Letters No.37, PP. 4433-4436, 1966. Pergsuon Press Ltd. Printed in Great Britain.

TEE COWPO~TIOW OF TPIMDTByLDWE SDLPHITS

Gordon Wood and PI. Miskow

Department of Chemistry, University of Windsor,

Windsor, Ontario, Canada.

(Received 3 June 1966)

Benzene as an @DIP solvent has been shown to exert a fairly

specific influence on the chemical shifts observed for protons

located near a carbonyl group in six-membered ring compounds. 1,233

In general the observed results are consistent with the formation

of a complex between the benzene and the positive contra of the

polar group.lp4 The axial groups generally lie within the region

of shielding while the equatorial groups are less shielded or

even deshielded.

We now wish to report that the proton spectrum of trimethylene

sulphite (I) is shifted by benzene in a manner not expected from

the conformational assignment made for this compound. Hellier5

adduced some evidence that (I) exists in a single conformation

and chose the chair form with S-O axial (Ia). Xowever, the

measured dipole moment for this molecule (3.5-3.6 D) does not

agree with that calculated for form (Ia) (1.8 D). Further, the

WWR spectrum was not assigned in detail and was anomolous in that

the assignments made placed the equatorial protons at higher

field than the axial. 6

4433

SIactra were raaured at 6OMcm on

roxmtir with the remits &own in the

Table

No.37

a JSOLJlW-C-60 spect-

Table.

Solvent Bffects on the NMR Spectrux of Trixethylene Sulphite

proton assignmenta C2(eg) C2(=) Cl,C3(eg) Cl,C3(=)

cDC13 ( lO$ w/V)b 8.38= 7.47 6.13 5.05

benzene (infinite dilution)d 9.6 8.5 7.0 5.6

A(benzene-CDCl3) 1.2 1.0 0.9 0.6

A(20$ henrene-CC14) 1.1 0.0 0.6 0.4

A(20$ beaueue-CC14) for (II)' @.951f 0.6~ 0.4h

a. b.

C.

d. 0. f. g. h.

As proposed in ref. 5. These chexical shifts do not differ appreciably from thsse found in CC14 or in the neat liquid. Chexical shifts are quoted in tau units from tetramthyleilane for the rid-point of each maltGet. Extrapolated from points at 30. 20, 10, aud 5s w/v. wso-Pentane-2,4-diol cyclic sulphite (isomer B, ref.10). cmultiplet reported for proton6 at C2. Value for CE group. Value for CJ group.

It can be seen that the protons are shielded by benzene to

a considerable extent and those protons labelled equatorial5 are

shielded more than those labelled axial. At least for the protons

at Cl and C3 this result ie opposite to that expected. The

shielding at C2 could depend in part on which side of the molecule

the benzene 8pproaches. This appears to be the case with the

1,3-dioxana studied by Anderson." PIa found that the C4 and C6

No.37 w3

axial protons ware l hiftd 0.3 pm upfield while the corre8-

pending equatorial proton8 were shifted only 0.2 ppa by ben*.ne.

The equatorial proton at C5 was shifted mubstantially mre than

the axial one (0.6 vr 0.3 ppm); thio result is consistent with

the approach of the benaene molecule froa the side opposite to

this axial proton.

When thi8 anomolou8 effect of the lmnrene solvent is added

to the considerable difficulties in interpretation of dipole

moment, RHR, and (in our handa) IR data8 for (I) it would aeex

to cast 8erious doubt on the a88ignmant of conformation (Ia).

Considering all the data presented up to now, the moat likely

conformation for trimethylene sulphfte appear8 to be the flexible

form (Ib). Waver, more evidence i8 needed before the earlier

suggestion9 of a chair-chair eguilibriux can be coxpletely ruled

out.

(Ia)

It i8 intereating to note that one of the

diol cyclic sulphites (II)" which has been a88igued the flexible

form shows, in benzene, behavior strikingly 8ixilar to that ob8erved

for (I). The last two lines of the Table 8how A value8 for theme

molecules under comparable condition8. The clo8e agreement is

4436 NO.J7

probebly fortuitoua end dependa, mng other thinga, on arbitrary

correlation of the iao multipleta repreaenting proton8 at Cl and

c. 3

Eowever, the other two ieomeric pentane-2,4-diol cyclic

aulphitea whose spectral propertiea are in good agreemant with

thoae anticipated for a chair conformation ahow benzene solvent

shifts two to five timaa smaller then (I)."

The authors wiah to thank the Wational Research Council of

Canada for financial aupport of thia work.

1.

2.

3.

4.

5.

6.

7.

0.

9.

10.

KS. Bhacca and D.H. Williema, Applications of BWR Suectroacopy

in Orqenic Chemistry, Chapter 7, Bolden-Day, San Francisco, 1964.

B.S. Bhacca and D.A. Williams, Tetrahedron Lettera, 3127, (1964).

D.H. Williama, e., 2305, (1965).

J.D. Co~olly end R. McCrindle, Chem. end Ind., 379, (1965).

D.G. Bellier, J.G. Tillett, H.F. VanWoerden, and R.FIW. White,

*., 1956, (1963).

For en attempt to interpret the WMR spectrum aee Yu. Yu. Samitov,

Dokladv Akademii Wauk SSSR, 164, 347, (1965).

J.E. Anderson, Tetrahedron Letters, 4713, (1965).

We have found that the IR spectrum of (I) in the region 1300-

1150 an -1

is sensitive tc solvent changes. For example, aub-

atitution of chloroform for carbon tetrachloride increases the -1

intensity of the 1230 cm band from about 12$ (relative to the

main band at 1190) to about 35s. Acetonitrile has a similar effect.

B.A. Arbouzov, Bull. aoc. them. France, z, 1311, (1960). -

~.C..Lauterbur, J.G. Pritchard, and R.L. Vollmer, J. Chem. Sot.,

5307, (1963). See alao C.G. Overberger, T. Kurtz, and

S. Yaroaiavaky, J. Org. Chem., 2, 4363, (1965). -

11. These measurements on (I) were made in 50$ benzene solutions

for comparison with the data of ref. 10.