Regio- and stereoselective synthesis of acetallic tetrahydropyrans as building blocks for natural products preparation, via a tandem [4+3]-cycloaddition/ozonolysis Process

A highly versatile synthetic pathway is presented for the preparation of polyfunctionalized acetallic tetrahydropyrans from conveniently substituted 1-methoxy-8-oxabicyclo[3.2.1]- oct-6-en-3-one derivatives, as intermediates in the total synthesis of natural and unnatural products with structural, functional and/or biological importance. This synthetic methodology involves two key steps: a [4 + 3] cycloaddition reaction between an oxyallyl cation and 2-methoxyfuran as a diene, followed by oxidative and/or reductive ozonolysis of the cycloheptenone subunit. This sequence renders polyfunctionalized 2-methoxytetrahydropyranic products capable of being easily opened under acidic conditions. The key steps, cycloaddition and subsequent ozonolysis were both fully studied under different reaction conditions and using several substrates in order to optimize yields and stereoselectivities and to study the scope of the methodology. It is noteworthy that both reactions proceed with high diastereoselectivity and, in the case of the oxidative ozonolysis, outstanding regioselectivity as well. A chemical library of 14 polyfunctionalized tetrahydrofurans, having five or seven stereocenters, has been prepared using the detailed approach

Versatile methodology to hydrate alkynes, in the presence of a wide variety of functional groups, with Mercury(II) p-Toluensulfonamidate, under catalytic, mild and neutral conditions

A method to generate carbonylic compounds from alkynes under mild and neutral conditions, with excellent functional group compatibility and high yields, is described. Hydration takes place under catalytic conditions by using from 0.1 to 0.2 equivalents of the easily available and inexpensive mercury(II) p-toluensulfonamidate in a hydroalcoholic solution. After use the catalyst is iner tized and/or recycled ..

Versatile methodology to hydrate alkynes, in the presence of a wide variety of functional groups, with Mercury(II) p-Toluensulfonamidate, under catalytic, mild and neutral conditions

A method to generate carbonylic compounds from alkynes under mild and neutral conditions, with excellent functional group compatibility and high yields, is described. Hydration takes place under catalytic conditions by using from 0.1 to 0.2 equivalents of the easily available and inexpensive mercury(II) p-toluensulfonamidate in a hydroalcoholic solution. After use the catalyst is iner tized and/or recycled ..