Organic synthesis with sulphones—XVII1

ORGANIC

SYNTHESIS WITH SULPHONES-XVIIt

THE ANTI-MARKOWNIKOFF HALOSULPHONYLATION VIA AN IONIC PATHWAY. AND A NEW METHOD BENZENESULPHONYL IODIDE

OF

OF OLEFINS PREPARING

L. M. HARWOOD, M. JULIA* and (in part) G. LE THU~LLIER Ecolc Normaic Su+ricurc.

Laboratoirc

de Chimie associc au C.N.R.S. No 32.24 rut Lhomond. Cedex 05. France

75231 Parts

Iodme and bromine in the presence of sodmm bcnzencsulphinatc react wtth olcfins in acetone Abstract solution to give halosulphones resultmg from an apparent steric direction of attack at the Intermediate halonium ion. A straightforward preparation of benzenesulphonyl iodide from benzenesulphonyl chloride and sodium iodide IS also described..

AreIlcsulphonyl iodides under the influence of U.V. light’ (’h or heat react wtth ofcfins by a radical pathway to give anti-Markownikof products I from which elimination leads to to-sufphonylatcd olefins (Scheme A). It has been shown that iodine in the presence of certain salts (eg. azides,’ acctatesj and thiocyanates’) and also iodine azidc’ and iodine isocyanatc6 react with olcfins to generally give Markownikoff addition products 2 via attack of the nucfeophile on an iodonium intcrmcdiate spcecies (Scheme 8). Exceptions have been observed however with severely stcrically hindered olefins such as t-butylcthylcnc6 It was reasoned that iodillati~~ll of olcfms in the presence of sodium areIlesu]phil~ates might similarly lead to

R*

ArSOi

t

\

I 1 R&S?’

AT

Markownikoff iodosulphonylation of olcfins (2, X = SO,Ar). This would lead, after dehydroiodinatioil. to vinylsulphones 3 isomeric with the products formed from the olcfin/arenesulphonyl iodide route. The electron dcficicnt double bond of vinylic sulphones undergoes a variety of nuclcophilic addition reactions’ and this modification therefore appeared to be a suitable method of reversing the polarity of terminal ofefins (Scheme C). The sulphonyl group could then bc readily removed by hydrogenolysis.’ Reaction of olcfins with a suspension of sodium benzenesulphinatc in a solution of iodine in acetone in the dark at room temperature Indeed led to the formation of ~~-iodosulphones. The direction of

I R’bOpr

%

R/c;‘;L/%+Ar

? +

AdO;

Scheme A

nucleophilic

reactivity

dectrophilic Scheme C

tPart XVI: .M. Julia. M. Ncl and Cheat.. 18 1. C 17 ( 1979 ).

L. Saussinc,

J.

Orguvo*nrfa/(ic

2483

reactivity

2484

L. M.

HARWOOD er al.

addition, as demonstrated by dehydroiodination was however found to be anti-Markownikoff (Table I). Control experiments showed that under thcsc conditions formation of benzenesulphonyl iodide did not take place, nor did benzcnesulphonyl iodide add to olefins. These results cannot therefore be explained by in situ formation of benzenesulphonyl iodide. With styrenes, hydroxysulphones and dehydroiodination products were also observed. Their formation is readily explained by further reaction of the reactive benzylic iodides. The structure of the /hydroxysulphone 9 obtained from r-methyl styrene was demonstrated by its spectral properties and its stability to oxidising agents, whereas 7, obtained from styrene. was identical with an authentic sample.’ Treatment of the iodosulphones 5 and 6 with triethylamine in methylene chloride at room temperature” led to the corresponding terminal vinyl sulphones in good yield. A similar reaction with bromine instead of iodine gave the corresponding /Sbromosulphones (again the products of anti-Markownikoff addition, Table II) accompanied by variable amounts of bromohydrins

(Markownikoff) and dibromides. The latter products, being stable under the reaction conditions, must therefore be true reaction products and not precursors to the bromosulphones. The /Gbromosulphones 11 and 14 were readily dehydrobrominated with triethylamine to give the terminally sulphonylated olefins. Oxidation of the bromohydrins 12 and 15 with pyridinium chlorochromate led to r-bromokctones. In the case of bromohydrin 15 the crude I-bromo-2-octanone obtained was contaminated with a small amount ( - 1“/oby N.M.R.) of 2-bromooctanal. This shows that the oxidation products of the anti-Markownikoff bromohydrins, being stable under the reaction conditions, would be detected if present. Regular formation of the anti-Markownikoff halosulphones is probably best explained by stcric reasons. Owing to its large size the sulphinate anion would not be able to reach the inner side of the iodonium ion and would thus have to attack at the terminal carbon atom. A similar argument has been invoked to account for the addition of iodine isocyanate6 and “abnormal” to t-butylethylene. Analogously iodonium nitrateI

Table olef in

0

addition

I. isolated yield W)

product

cr I

I

20

‘*S02Ph

4

48

~SO2Pl.F I

5

phk

S02Pha

ph%S02phb

24

ph~SO2p:

14

13

8

s OH Ph<

SO2&

19

S02Ph

Ph JL

20

10

s

1 n

a)Gives

tm

RCH=CHSO2Ph with base

b) Previously reported’

c)Resists oxidation

Table II. addition

oletin

isolated

product

f

nCliH13*

nCsH13/\S02ph

nC&3-Br

-14

5

32

nC6H,3’\Br 16

.’ -

d) Previously g)Cives

tx

reported

11.13

c) Oxidized

RCH=CHSO2Ph

to

with base

a-bromoketone

f ) Previousb

reported

12

yie! j

’

2485

Orgamc synthcsls with sulphones-XVII

chlorides add in an anti-MarkownikotT fashion to t-butylcthylene15 and bulky nucleophiles are known to attack styrene oxide at the terminal carbon atom.” There are apparently no such restrictions on attack of the bromonium species by water as cvidcnced by the constitution of the bromohydrins obtained. (Scheme D). From a preparative point of view the above results show no advantage over the very efficient U.V. catalysed addition of benzenesulphonyl iodide to olefins. This reagent is readily available through the reaction of sodium benzenesulphinate with iodine.17 As the former is usually prepared by reduction of benzencsulphonyl chloride” and the latter by oxidation of iodides. the possiblhty of preparing bcnzenesulphonyl iodide directly by reaction of bcnzcnesulphonyl chloride with an inorganic iodide. appeared to be worthy of investigation. Early reports “)‘.” mention the formation of sodium benzencsulphinate and iodine when benzenesulphonyl chloride is added to a solution of sodium iodide in acetone (Schcmc E). This appeared to bc a suitable way of securing both reagents necessary for the preparation of benzcnesulphonyl iodide. arylsulphcnyl

PhSOzCl + ZKal-

-+ PhSO,Na

from the initially homogenous reaction mixture was found to consist only of sodium bcnzenesulphinate and the use of slightly more than 3 equivalents of sodium iodide was necessary for 100’~~yield of the salt (Table III). The dark solution obtained after filtration and addition of pentane yielded a black solid which was filtered and extracted with chloroform. Removal of the chloroform gave a dark solid which was recrystdllised from acetone giving black hygroscopic lustrous needles. The product readily evolved acetone on gentle heating. N.M.R. dosage of the freshly prepared product indicated six moles of acetone to be contained in each mole of complex. On stronger heating iodine monochloride was evolved, characterised by its boiling point (found 97-IOO”, Lit.” 97.4”), and demonstration of the presence of chloride and iodide in an aqueous solution. These facts have led us to formulate the crystalline product as 17: the stoichiometry of the reaction is indicated in Scheme F. The complex proved to be too unstable to obtain an acceptable elemental analysis.

+ I, + NaCl

Schcmc F

Schckc E

Attempts to treat olefins directly with the reaction mixture did not lead to the formation of /Iiodosulphones: a surprising result in view of the fact that iodine and sodium benzenesulphinate have been shown to react readily with olefins. We therefore reinvestigated the benzenesulphonyl chlorideisodium iodide system. The white solid which separated slowly

An aqueous solution of 17 is rapidly decolourised by thiosulphate hence providing an explanation of the previous erroneous assumption of the presence of iodine. ’ gaCompound 17, unlike iodine monochloride is not reactive towards olefins. A nucleophilic species l,CI- ” might be responsible for this. Admixture of aqueous solutions of 17 and sodium benzenesulphinate leads to instantaneous formation of

Table 111

4

Nal PhSO, CL (equivalents)

Organic

syntheses with sulphones XVII

reddish brown colouratton and the slower formation of a white precipitate. After 3 h at ambient temperature the mixture was filtcrcd. washing the residue with acetone (2 x 30mlj. to give pure sodium benzmcsulphinate (6.60g. Yield: quantitative). Pentanc (4UOml) was added to the filtrateand the resultant voluminous black precipitate filtered and t&mated with methylenc chtoride (3 x 75 ml) to give a brown solution lcavmg behind a grey rcstduc (2.9Og) shown to bc crude sodium todtdc. Evaporatton of the solution at reduced pressure gave a dark powdery solid which was recrystallised rapidly from acetone under a mtrogcn atmosphere to give the complex 17 as hygroscopic lustrous black needles (19.4og.y&d: 61 ‘tv )) Gentle heating caused loss of acetone from the sohd which was best stored at 0°C under a slrght positive pressure of dry mtrogcn. The spectral data of this complex are identical with those of acetone. Prepurutron of he~~;e~~e.srtlphotr~l iodide using complex 17 A solution of complex 17 (5.38g. 6.7 mmoles) in distilled water (20ml) was added raptdly to a solutron of sodium benzcncsulphinate (1.31 g) in distilled water (20ml). The instantaneously formed precipitate was filtcred and the cream solid thus obtained dried in rucun in darkness (1.41 g. yield: 79”,,). One recrystallisation from carbon tctrachlortde gave large yellow nccdhs mpt. 45-h” (Lit.‘; 44-S”). ~~~~f~k~~~dg~~rn~~f We thank the Royal Society and the Centre Nation& do La Rechcrche Screnttfique for the award of a fellowshtp under the European Sctcnce Exchange programme (to L.M.H.).

REFERENCFS ’ .‘P . S Skell and J. H. McN~~rna~. J. .4rner. Chart. Sttr. 79.85 (lY57); “S. J. Cristol and 5. I. 5avres.J. Org. C‘ketn. 29, 1281 (1964). ‘R. C. Cambie. R. C. Hayward, P. S. Rutledge. T. SmithPalmer and P. 5 Woodgate. J.C.S. Per/&r I. 840 (1976). ‘R. C. Cambic. B. G. Lindsay. P. S. Rutledge and P. 5 Woodgate. Ihfc/ X45 (lY76).

2487

‘R. C. Cambie, Ho H. Lee, P. S. Rutledge and P. D. Woodgate. /hid. 757 (IY79) and references cited therem. ‘R. C. Cdmbtc. R. C. Hayward, P. S. Rutledge, T. SmithPalmer, B. E. Swedlund and P. D. Woodgatc. Ibid. 180 (1979) and references cited therem. “A. Hassner, R. P. Hoblitt, C. Heathcock, J. E. Kroppand M. Lorbcr. J. .4n1rr. Chrtn. So<. 92, 1326 (1970). -‘For instance by. CN‘. L. Horner. W. Hofer. I ErteI and H. Kunz C‘hem. Ber. 103, 2718 (lY70): R,N. W. G. Davtcs. E. W. Hardisty. T. P. Ncvcll and R. H. Peters. J. Chew. SW. (E) 1004 (1970): EtO‘. L. M. Harwood and M. Julia. ~Ilpublished results ‘For example by: aiummtum amalgam. V. Pas&t and A. Umam-Ronchi. C/tern. Conrn~ro~. 35 1 (1973 ): dithtonitc:dimcth~lformam~de. M. Julia. 5. Launay and J. Bremner, unpubhshed results. ‘M. Julia.and J. M. Paris. 7i’trdwdrm I.rrrws 4833 (1973). “‘W . F_.Truce and C. T. Cjordlskl. .I. Org. C/tern.. 36. 2536 (1971). ’ ‘L . I. Zakharkin and Ct. G. Zhtgareva. Zh. Org. I
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