Methanetetraboronic and Methanetriboronic Esters as Synthetic Intermediates

Methanetetraboronic and methanetriboronic esters constitute a new type of one-carbon synthon which bears some analogy both to malonic ester and to Wittig reagents. These reagents show promise of extending the utility of organoboron chemistry to classes of compounds that are not compatible with hydroboration reactions. 1. Preparation of Methanetetraboronic and Methanetriboronic Esters 1.1. The Preparative Method 1.2. Scope of the Synthesis 1.3. Cyclic Boronic Esters 2. Tris[dialkoxyboryl]methide and Bis[dialkoxyboryl] methide Anions 3. Condensation of Di- and Triborylmethide Ions with Aldehydes and Ketones 3.1. Methoxyboron Compounds 3.2. Cyclic Boronic Esters 3.3. Mechanistic Considerations 3.4. Synthetic Significance 4. Alkylation of Di- and Triborylmethide Ions 4.1. Tris[trimethoxyboryl]methide and Bis[dimethoxyboryl]-methide 4.2. Cyclic Boronic Esters 5. Metallation of Di- and Triborylmethide Anions and of a Tetraborylmethane 5.1. Introduction of one Group IV Substituent 5.2. Introduction of two or three Group IV Substituents 5.3. Tetrakis[acetoxymercuri]methane 6. Halogenation of Di- and Triborylmethide Ions 6.1. Bromotris[dialkoxyboryl]methanes 6.2. Other Halo Compounds