The present invention relates to bi- and tricyclic compounds of the general formula (I) (I) wherein the dashed lines independently of each other represent a single or a double bond, X represents a group of the formulae X.sub.1 to X.sub.3 wherein the asterisk denotes the point of attachment to the rest of the molecule, R.sup.1a and R.sup.1b, independently of each other, are selected from hydrogen or methyl, or R.sup.1a together with R.sup.1b with R form a methylene or ethylene group, R.sup.2, R.sup.3a, R.sup.3b, R.sup.4, R.sup.5a and R.sup.5b, independently of each other, are selected from hydrogen or methyl, R.sup.6 is selected from hydrogen, methyl or ethyl, and R.sup.7 is methyl or ethyl, to a method of preparing said compounds, to the use of a bi- or tricyclic compounds or of mixtures of two or more bi- and tricyclic compounds or of a stereoisomer thereof or of a mixture of two or more stereoisomers thereof as aroma chemicals; to the use of a bi- or tricyclic compound for modifying the scent character of a fragranced composition; to an aroma chemical composition containing a bi- or tricyclic compound or a mixture of two or more bi- and tricyclic compounds or of a stereoisomer thereof or of a mixture of two or more stereoisomers thereof; and to a method of preparing a fragranced composition or for modifying the scent character of a fragranced composition, comprising incorporating a bi- or tricyclic compound or a mixture of two or more bi- and tricyclic compounds or of a stereoisomer thereof or of a mixture of two or more stereoisomers thereof into said composition.

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A process for the preparation of a class of molecules, namely bicyclo[1.1.1]pentanes and derivatives thereof by reaction of [1.1.1]propellane with a variety of reagents under irradiation and/or in the presence of radical initiators to obtain bicyclo[1.1.1]pentanes asymmetrically substituted at position 1 and 3, which are useful as intermediates for the preparation of asymmetrically 1,3-disubstituted bicyclo[1.1.1]pentane derivatives and various physiologically active substances or materials containing these structures.

A process for the preparation of a class of molecules, namely bicyclo[1.1.1]pentanes and derivatives thereof by reaction of [1.1.1]propellane with a variety of reagents under irradiation and/or in the presence of radical initiators to obtain bicyclo[1.1.1]pentanes asymmetrically substituted at position 1 and 3, which are useful as intermediates for the preparation of asymmetrically 1,3-disubstituted bicyclo[1.1.1]pentane derivatives and various physiologically active substances or materials containing these structures.

A process for the preparation of a class of molecules, namely bicyclo[1.1.1]pentanes and derivatives thereof by reaction of [1.1.1]propellane with a variety of reagents under irradiation and/or in the presence of radical initiators to obtain bicyclo[1.1.1]pentanes asymmetrically substituted at position 1 and 3, which are useful as intermediates for the preparation of asymmetrically 1,3-disubstituted bicyclo[1.1.1]pentane derivatives and various physiologically active substances or materials containing these structures.

A process for the preparation of a class of molecules, namely bicyclo[1.1.1]pentanes and derivatives thereof by reaction of [1.1.1]propellane with a variety of reagents under irradiation and/or in the presence of radical initiators to obtain bicyclo[1.1.1]pentanes asymmetrically substituted at position 1 and 3, which are useful as intermediates for the preparation of asymmetrically 1,3-disubstituted bicyclo[1.1.1]pentane derivatives and various physiologically active substances or materials containing these structures.