Reagents boron-based

Using boron-based reagents Chlorodiisopinocampheylborane, 72 Lithium triethylborohydride, 205 Sodium cyanoborohydride-Tin(II) chloride, 280... 

Brown and co-workers developed a novel homoallenyl boronate reagent 169 based on diisopropyl tartrate for the stereoselective homoallenylation of aldehydes 170. The reagent 169 was prepared via homologation of the corresponding allenyl boronate or the alkylation of halomethyl boronate with allenyl Grignard similar to those reported in Scheme 26. The allyl boronate 169 upon reaction with aldehydes furnished the dienyl alcohols 172 with high ee (Scheme 28) <1996JOC100>. 

In addition to being useful reagents for the reductions of carbonyl compounds, boron-based reagents can also be used for the conversion of an alkene to a wide variety of functionalized alkanes. Because the majority of these reagents carry a terpene substituent, they are discussed under these chiral pool materials (Chapter 5). 

Potentially useful asymmetric reduction using boron-based reducing agents involves stoichiometric and catalytic processes.1060,1061 Of the stoichiometric reagents reported, those that are the most promising for the highly enantioselective reduction of various functionalized ketones are 532,1062 533,1062 48a,1063-1065 534,1063,1066-1071 anc 535 (Scheme 41).1061... 

The reduction of various carbon-nitrogen ir-systems to saturated derivatives with metal hydrides, principally aluminum- and boron-based reagents, provides highly useful processes for the preparation of amines and related functionalities. 

The reduction of a carbonyl group to an alcohol has been achieved at a laboratory scale with a large number of reagents, many stoichiometric with a ligand derived from the chiral pool. The development has culminated in boron-based reagents that perform this transfonnation with high efficiency (Chapter 11). 

Reagent chemistry based on boron has seen some advances. Tetra-... 

Development of boron-based reactions and reagents for organic synthesis, particularly, of heterocycles 07Y1048. 

Figure 22.6 Boron-based monomers 14, 15, and 19-22 and reagents 16-18 for the incorporation of the pinacol-boron group into monomers.

In addition to Ullmann s copper-catalyzed [107] C(spVN bond formations using haloarenes, a remarkable complementary approach was developed by Chan and Lam during the 1990s using boron-based arylating reagents [108, 109). A detailed review by Andrew W. Thomas and Steven V. Ley on these oxidative copper-mediated and copper-catalyzed arylations, as well as their extension to alcohols [108, 110], is to be found in Chapter 4. 

Copper-Catalyzed Arylations of Amines and Alcohols with Boron-Based Arylating Reagents... 

This chapter will attempt to summarize selected key learnings and trends, and will also highlight recent developments of these methods solely devoted to the copper-catalyzed oxidative arylations of O—H and N—H bonds with boron-based arylating reagents. Further, it will detail some specifics that have brought the method to its current high levels of popularity within the synthetic organic chemistry community. 

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