Decynyl(phenyl)iodonium Tetrafluoroborate1

[102987-32-6]  · C16H22BF4I  · Decynyl(phenyl)iodonium Tetrafluoroborate  · (MW 428.06)

(used in cyclopentene annulation;3,4 can function as alkynyl equivalent5 and vinyl cation equivalent6)

Physical Data: mp 59.5-65 °C.

Preparative Methods: best achieved in 85% yield by reaction of (1-decynyl)trimethylsilane with excess Iodosylbenzene and Boron Trifluoride Etherate, and subsequent treatment with excess aqueous NaBF4 solution (eq 1).2 This method provides a general route for the synthesis of alkynyl(phenyl)iodonium tetrafluoroborate salts from alkynyltrimethylsilanes.

Introduction.

Alkynyl(phenyl)iodonium salts are highly electron-deficient species of formal tetraphilic nature (Ca, Ca, Cb, and I) towards nucleophilic attack.

Nucleophilic Attack At Cb.

Despite the wide scope for nucleophilic attack on alkynyl(phenyl)iodonium tetrafluoroborates, only reports of Cb attack have been detailed to date for 1-decynyl(phenyl)iodonium tetrafluoroborate.

The reagent has been employed3 in cyclopentene annulations, by a process referred to as tandem Michael-carbene insertion, through reaction of the stabilized anion of 1,3-diketones and 1,3-diesters (eq 2). The reaction proceeds, with concomitant reductive elimination of iodobenzene, via an alkylidenecarbene intermediate which subsequently undergoes an intramolecular 1,5 C-H insertion reaction.

Similar transformations have been studied4 with heteronucleophiles to give functionalized cyclopentenes (eq 3).

The use of alkynyl(phenyl)iodonium salts as alkynyl cation synthetic equivalents has been amply demonstrated.5 In addition, treatment of 1-decynyl(phenyl)iodonium tetrafluoroborate with Azidotrimethylsilane generates6 the b-azidovinyliodonium salt (eq 4). Salts of this type behave as vinyl cation equivalents in nucleophilic substitutions owing to the high leaving group potential of the hypervalent iodine(III) substituent, the use of which has been reported7 in the synthesis of a variety of alkenes including a-cyano, a-nitro, vinyl sulfides, and a,b-unsaturated esters.

a-Acyloxy ketones have been synthesized8 from 1-decynyl(phenyl)iodonium tetrafluoroborate under both basic and acidic conditions. Treatment of the reagent with excess sodium acetate in THF/H2O gave 1-acetoxy-2-decanone in 78% yield (eq 5). The use of water is reported as essential for the reaction to proceed effectively.

1-Acetoxy-2-decanone is also produced in 86% yield by refluxing the reagent in acetic acid for 15 h. Syntheses and uses of a-acyloxy ketones have been previously demonstrated.9


1. For reviews of alkynyl(phenyl)iodonium compounds, see (a) Stang, P. J. AG(E) 1992, 31, 274. (b) Moriarty, R. M.; Vaid, R. K. S 1990, 431.
2. Ochiai, M.; Kunishima, M.; Sumi, K.; Nagao, Y.; Fujita, E.; Arimoto, M.; Yamaguchi, H. TL 1985, 26, 4501.
3. Ochiai, M.; Kunishima, M.; Nagao, Y.; Fuji, K.; Shiro, M.; Fujita, E. JACS 1986, 108, 8281.
4. Ochiai, M.; Kunishima, M.; Tani, S.; Nagao, Y. JACS 1991, 113, 3135.
5. Ochiai, M.; Uemara, K.; Oshima, K.; Masaki, Y.; Kunishima, M.; Tani, S. TL 1991, 32, 4753.
6. Ochiai, M.; Kunishima, M.; Fuji, K.; Nagao, Y. JOC 1988, 53, 6144.
7. Ochiai, M.; Sumi, K.; Nagao, Y.; Fujita, E. TL 1985, 26, 2351.
8. Ochiai, M.; Kunishima, M.; Fuji, K.; Nagao, Y. JOC 1989, 54, 4038.
9. Rawlinson, D. J.; Sosnovsky, G. S 1973, 567.

Richard Wisedale

University of Bristol, UK



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