The conversion of ortho-hydroxylated Mannich bases to the corresponding methylated compounds, e.g., cresols, can be effectively carried out using a novel hydrogenation technique.
A Mannich base intermediate for 2-[(4-heterocyclic-phenoxymethyl)-phenoxyl]-alkanoates and methods for its preparation are provided. A method for preparation of an alkyl 2-[2-(secondary amino methyl)-5-alkylphenoxy]-alkanoate comprises the steps of: reacting a mixture of m-alkyl phenol, a secondary amine, and an aldehyde, with or without a catalyst, in a first solvent at reflux temperatures to form a 2-[(secondary amino)methyl]-5-alkylphenol. That product is then reacted with an alkyl 2-haloalkanoate, and an alkali metal carbonate, with or without a second catalyst in a second solvent at reflux temperatures to form the 2-[2-(secondary amino methyl)-5-alkylphenoxy]-alkanoate. The aldehyde may be paraformaldehyde, aqueous formaldehyde, formaldehyde, or polymerized acetal derivatives thereof. The first solvent may be acetonitrile or toluene. The catalyst may be an acid catalyst or a base catalyst. In the preferred embodiment the Mannich base is a 2-[(secondary amino)-methyl]-5-alkylphenol, or a 2-[2-(secondary amino methyl)-5-alkylphenoxy]-alkanoate.
In a multi-chip module, a structure for selectively connecting two conductors. A switchable connector (36) is disposed between a first and second portion (30,32) of a copper conductor (28). The switchable connector comprises an amorphous silicon layer (58), which extends between two spacer pads (56) that are electrically connected to the first and second portions of the copper conductor. A barrier layer (60) is formed atop the amorphous silicon, physically separating it from a reactive metal layer (62). The reactive metal layer is coated with an antireflective coating (64). Interaction of the reactive metal layer with the amorphous silicon layer is prevented by the barrier layer until the barrier layer is heated above 500.degree. C. A laser beam (66) is focused on opposite edges of the switchable connector, causing the barrier layer and reactive metal layer to diffuse into the amorphous silicon, forming electrically conductive silicides. Electric current can then flow between the first and second portions of the copper conductor through the silicides and the remainder of the reactive metal layer.
