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Cyclization of Homoallylic Alcohols with Iodine/Iodine(III) 

Paulo Scarassati and Luiz F. Silva Jr.*

Instituto de Química, USP, CP 26077, CEP 05513-970, São Paulo SP, Brazil  

scarpaulo@hotmail.com and *luizfsjr@iq.usp.br  

Tetrahydrofurans compounds can be obtained by cyclofunctionalization

of homoallylic alcohols.1  Many electrophiles have been used, such as

halogens, thallium(III), mercury(II), selenium, etc.1 The iodocyclization of

homoallylic alcohols with terminal double bonds leads to the formation of

oxetanes,2  because the 5-endo-trig   cyclization is not favored for these

substrates. The use of hypervalent iodine with a catalytic amount of

molecular iodine possibilitates the formation of THFs rings from

homoallylic alcohols (Scheme 1).3

This methodology can serve well for obtaining substituted

tetrahydrofurans starting from primary and secundary homoallylic alcohols.

CONCLUSION

a 2 equiv of HTIB, 0.2 equiv of I2, MeOH, rt, overnight; b ratio between diasteromers

REFERENCES

Table 1. Reaction of 6a-e with I2/HTIB

RESULTS AND DISCUSSION

Figure 1. Color before and after the reaction completion

FAPESP, CNPq and CAPES for financial support

1. Jalce, G.; Franck, X.; Figadére, B. Tetrahedron: Asymmetry  2009, 20,

2537.

2. Evans, R. D.; Magee, J. W.; Schauble, J. H. Synthesis 1988, 11, 862.

3. Vasconcelos, R. S.; Silva, L. F., Jr; Giannis, A. J. Org. Chem. 2011, 76

1499. 

ACKNOWLEDGEMENTS

6a-d were prepared as reported (Scheme 3), whereas 6e  is

commercially available. The reaction of the homoallylic alcohols 6a-e with

HTIB and I2  led to the formation of the desired products (Table 1). The

diasteromer ratio was determined by GC or NMR. No significant

stereoselectivity was observed for 6a-d, but for substrate 6e, the 

reaction is stereospecific.  The cylizations can be easily monitored bycolor change (Figure 1). 

Scheme 1. Iodocyclization of homoallylic alcohols

Scheme 3. Preparation of starting materials 6a-d 

INTRODUCTION

The reaction of 1  initially originated two differents compounds (2a-b)

that led to the desired tetrahydrofuran 5. Interrupting the reaction in the

beginning, it was possible to characterize these intermediates. Theproposed mechanism (Scheme 2) is divided into two routes: a) Attack of

external MeOH (2a) or b) Attack of internal hydroxyl group (2b) to the

iodonium intermediate. The oxidation of alkyl iodides (2a-b) by HTIB

(PhI(OH)OTs) gives the corresponding I(III) species, which is a

hypernucleofuge. In route a, intramolecular attack of the hydroxyl group

to the I(III) moiety of 3a gives 5. In route b, the displacement of iodine

group by oxygen leads the bicyclic oxonium ion 4. MeOH attacks giving 5. 

Scheme 2. Mechanism for I2/Iodine(III) cyclization

Keywords: Homoallylic Alcohols, Cyclization, Hypervalent Iodine, Tetrahydrofurans