β-Acyloxysulfonyl Tethers for Intramolecular Diels−Alder Cycloaddition Reactions

Abstract

[reaction: see text]. beta-Hydroxy sulfone-based tethers were employed for the first time to achieve thermally mediated intramolecular Diels-Alder cycloaddition. The reactions proceeded with complete regioselectivity and high (10/1) to complete endo/exo-selectivity and resulted in the preferential formation of one of the two possible endo-cycloadducts. The yields and stereoselectivities were proportional to the bulk of the R(1) substituent on the beta-acyloxysulfonyl tether.

(4aSR,7SR,9aSR)-7-tert-Butyl-9a-methyl-5,5-dioxo-1,2,4a,9a-tetrahydro-8-oxa-5λ6-thiabenzocycloheptan-9-one

“…The title compound was synthesized as described by Chumachenko et al (2005) as a mixture of the exo-and two endo-cycloadducts, viz. (I), (II) and (III), in a ratio of 12/100/4, as established by 1 H NMR of the crude reaction product.…”

1-[(E)-Butadienylsulfonyl]-3,3-dimethylbut-2-yl methacrylate

“…The title compound, (I), was synthesized as described by Chumachenko et al (2005). Single crystals were grown as large colourless blocks from a toluene solution by slow cooling to 278 K. )/3 (Á/) max < 0.001 Á max = 0.45 e Å À3 Á min = À0.24 e Å À3 Table 1 Selected bond lengths (Å ).…”

“…The title compound, (I), was prepared as part of a study of the potential utility of sulfone-based tethers in intramolecular Diels-Alder cycloaddition reactions (Chumachenko et al, 2005). Its structure in the solid state has been established at 100 K by single-crystal X-ray diffraction.…”

(4aSR,7SR,9aRS)-9a-Bromo-7-methyl-5,5-dioxo-1,2,4a,6,7,9a-hexahydro-8-oxa-5λ6-thia-1,4-benzocyclohepten-9-one

“…In several cases, we were able to crystallize the major and/or minor diastereomeric cycloadducts in a form suitable for analysis using single-crystal X-ray diffraction. Details of the synthesis of the cycloadducts will be reported elsewhere (Chumachenko et al, 2004). In the present paper, the solid-state structure of the title cycloadduct, (I), as established by single-crystal X-ray diffraction methods, is described.…”