| The synthesis and use of boronic acids play a central role in modern organic chemistry. Despite a significant amount of work in this area, free boronic acids are still relatively difficult to synthesize and purify. A solid phase strategy for the synthesis and purification of boronic acids is presented in Chapter 2. This strategy relies on the use of DEAM-PS resin as an efficient support to immobilize and derivatize arylboronic acids. Using this solid support, a wide range of boronic acids can be accessed through nucleophilic substitution, reductive amination, amide coupling, urea, thiourea, and anilide formation, as well as Ugi four-component coupling.; The use of diisopinocampheylborane for the synthesis of E-alkenylboronic acids is presented in Chapter 3. Hydroboration with this easily accessible reagent, followed by oxidation with acetaldehyde, hydrolysis, and trituration in hexanes generates E-alkenylboronic acids of very high purity. The products made available by this method are useful precursors for cycloaddition reactions of alkenylboronates, among other applications.; Chapter 4 describes a resin-to-resin Suzuki coupling methodology. This strategy allows for the convergent synthesis of biphenyl compounds, some of which would be difficult to make via a traditional linear approach. A small parallel library of biphenyl compounds was made using an automated synthesizer, illustrating the usefulness of a resin-to-resin strategy in combinatorial chemistry.; The development of a method for the asymmetric addition of allylboronates to aldehydes under Lewis acid catalysis is presented in Chapter 5. Using camphor-derived allylboronates, this method has several advantages over existing methodologies. Significantly, it combines important features such as stability of the reagents, wide substrate scope, and very high diastereo- and enantioselectivity. On a practical level, it proves to be useful for the stereoselective synthesis of gram quantities of homoallylic alcohols.; Finally, Chapter 6 presents our efforts in the area of cycloaddition reactions using alkenylboronic acid-diethanolamine adducts. Despite the disappointing results, this study underlines the importance of having easy access to free boronic acids in their pure form. In this regard, it provides an interesting link with the research described in Chapters 2 and 3. |
