Tetrahedron Letters No.38, PP. 2685-2689, 1964. Pergamon Press Ltd. Printed in Great Britain.

NEIGBBOUFIINO GROUP PAETICIPATICN BY SmsHIRpzrOXTGEN

Istitnto di Chimica Organica dslltUnivereitB, Podena, Italy

Ft. Danieli, H. Hogeveen,+ and 0. Macoagasni

Istituto di ChMoa Ormica e Induetrlale dellYM.rereith,

Laboratorio C.R.B., V (Iruppo di Ricema, Bologna, Italy

(Received Y August 1964)

Participation by sul-l-oxygen 8s neighbouring group has been

previously found (1,2) in iodolactonisatlon (iodine and aodium hydrogen

carbonate In ohlorofom-water) of sgn-3-~phenylsulph~~lblcyclo[2,2,1]

hept-5-ene-P-endo-carboxylio eeid (I-a). This acid yielda 35% of the iodohydrin

(III-a) together with the azpected icdolactone, rhilo the anti-isomer (II),

as well as the correspondent sulphide and sulphone, yield only the lodolac-

tonea. The iodohydrln (III-b) is the only product from the _syPester (I-b).

It haa been shown that the reaction proceeda through an inversion at the

aulphur atom (2). In I8 0 enriohed water isotopic exchange at the SO group

was observed (2), while noue occurred at the OH group.

* Present addresa: Konluklijke/Shell-Lsboratorlum, Amsterdam, The Netherlands

2686 Neighbooring group participation by sulphinyl-oxygen No.38

(II) (1x1-8) B - H

(III-b) B I CH 3

I

A co CH

2 3 OLS-Ph I-

3

(VI

The axgerimentsl results suggest the existence of a transition state

of type (IV), with neighbouring group participation by sulphinyl-orygen,

nuoleophilic substitution at sulphur, and Walden inversion. Compound (V),

m.p. 1410 dso., is isolated osrring out the reaction in ethanol or in a

concentrated solution of water; srceas of eater converts compound (V) to

the lodohydrin (III-b) Lfoundr C 23.00; H 2.22; 165.30; C H I 0 S 15 16 4 3

requires: C 22.98; H 2.06; I 64.76; A_(C2H4C12) - 295 and 365 mn,

characteristic peaks (3) of the I - 3

ion; no absorption was detected, nujol

-I and acetonitrile, in the lOOC-1200 cm region (SO stretching)].

On the basis of these results and of the ligand properties of aulph-

culdes, which generally are due to the oxygen atae (4), other cases of

neighbouring group participation by aulphinyl-orggen might be anticipated:

indeed, a few examples have recently been reported (5).

NO.38 Neighbouring group participation by sulphinyl-oxygen 2687

We directed our attention to sulphoxidea in which the sulphinyl-aqgen

might pravido anchimerio assistance iar unimolecular nucleophilic subatitut1on.s

through a ring intermediate. The rate0 of aolvolysi~ in 8o+aqueone ethanol

(v/v) of tertiary ohlorO-d*rivativos Ph-x-(cH,)pc(cE3),cl, x I so, s, so*,

n = 1,2,3, were measured. The solvolphs reactions were followed br oonduotaw-

trio measurements et least up to 75$-Oo~vsrsion, first-order constants being

derived by Ouggenhrim's method (6). The rate constanta are reported In Table 1.

TABLE 1

Bates 0f t30i~0lpif~ in aog-etbanol at 35.00 (kl x id ~100.") of

Ph-X-(CH2)n-C(CH3)2C1

x I so x-s x - so 2

162 125 0.15

193 0.87 0.54

37.1 2.36 O.PP

(CH3)3C-cl 8.0

All sulphcaddes examined react faster than the parent aulphides; the

rate la maximum when n - 2, to say for a cyclic 5 membered intermediate.

The sulphides rate sequence (13 >&>y) is the same (7) ae that observed

for ths correspondent primary derivatives: in both primary and tertiary series

2688 Neighbmlrlng group participation by sulphinyl-oxygen U0.V

neighbouring group participation by eulphur is particularly strolig for the

P-derivative. The values found for the sulphonea, !3 < y<:6<t-But-Cl, can

be explained on the basis of the inductive effect of the SO2 group tranemitted

through the carbon chain. The bydroxy-eulphoxidsa are the products from the

hydrolysis of cbloro-sulphoxidos in 5O$-vatex-dimane.

Chloro-eulphides were obtained from the parent hydrany-sulphidee and

anhydrous hydrochloric acid in chloroform solution; bxdraxy-sulphides from

thiophenol aad the chlorohydrins Cl-(CH2)n-C(CB ) -OH. 32

Cbloro-stipharidea

were likewise prepared from the parent hydroxy-sulphoxides, while chloro-

TABLE 2

compounda

Ph-X-CH2-C(CH3)2-T

II

n

n

X

s

S

so

so 2

s

SO

so2

S

so

so2

Y m.p.

Cl

OH

OH 117-1180(s)

Cl 44-450(a)

OH

OH

Cl

OH

OH

Cl

84-859(e)

b.p./mm.

59-600/13

136-1370/12

ilO-1130/0.7

162-1640/0.8

153-1554/l

129_130"/1

1.5661

1.5609

1.5573

1.5380

1.5511

1.5320

(a) from bemzens.

No.78 Neighbcuring group participation by sulphinyl-oxygen 2689

-aulphones wsre best obtained by midising &loco-sulphides with perbeneoic

acid.

Chlorc-sulphaides and -sulphides are liquid compounds, which generally

decompose by distillation in vacuurm: therefore thsy were employed for kinetic

measurements as crude prcducts, without further purification (elemental

analyses being always satisfactory). The physical constants of chlorc-aulphones,

hydroxy-sulphoxides and -s ulphides are reported in Table 2.

This work was supported by a grant from the Consiglio Nazionale delle

Ricsrche, Rome.

1.

2.

3.

4*

5.

6.

7.

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