Application of Hemithio Ketene Acetals to the Synthesis of Spirocyclic Orthoesters

Abstract

Spirocyclic orthoesters have been synthesized by a method that employs a hemithiophenyl ketene acetal as an orthoester precursor. The orthoesters can be generated in good yields and under mild reaction conditions.

orthoesters - spiro compounds - synthesis - acetals - thioketene acetals

References

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<A NAME="RS04204ST-2A">2a</A> Hemithioketene acetal 4 was synthesized using a published method: Brandsma L. Schleyer P. Verkruijsse HD. J. Organomet. Chem.  1987,  332:  99 

<A NAME="RS04204ST-2B">2b</A>

The ¹³C NMR spectrum of hemithio orthoester 6 has characteristic resonance signal at δ = 109.7 ppm.

<A NAME="RS04204ST-2C">2c</A>

Two ¹³C NMR resonance signals at δ = 169.7 and 171.6 ppm were observed.

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<A NAME="RS04204ST-4">4</A> Hemithio ketene acetal 7 was synthesized using a published method: Boeckman R. K., Bruza K. J.; Tetrahedron; 1981, 37: 3997

<A NAME="RS04204ST-5">5</A>

Deactivated silica gel refers to silica gel that was first treated with Et₃N, and then washed with the desired eluent.