Diboration aldimines

Commercially available Pt(cod)Cl2 catalyzes the diboration of alkenes, alkynes, and aldimines using bis(catecholato)diborane(4) (cod =1,5-cyclooctadiene). Catalyzed aldimine diboration provides the first direct... 

Commercially available Pt(cod)Cl2, catalyzes the diboration of terminal aikenes, vinylarenes, and alkynes using B2cat2 to give compounds 92-96 in excellent yields (Scheme 17).68 The first metal-catalyzed diboration of aldimines to form. R-amino boronate esters was also obtained when Pt(cod)Cl2 was used. 

Following advances made in reduction reactions (vide supra), hydroboration and diboration have been the subject of intense investigation with NHC-Cu catalysts. Early work by Sadighi revealed that [(ICy)Cu(Ot-Bu)] efficiently catalyzed the 1,2-diboration of aldehydes. Mechanistic studies permitted to rationalize a number of features of this reaction and notably ruled out a possible oxidative addition pathway to favour c-activation of the diboron reagent by the copper centre. [(ICy)Cu(Ot-Bu)] was also used for the diaster-eoselective diboration—in fact, hydroboration after work-up—of sulfinyl aldimines. ... 

In general, the diboration of alkenes with [Pt(dba)2] required 50 while the use of [Pt(NBE)2] or [Pt(COD)2] (NBE = norbomene, COD = 1,5-cyclooctadiene) as precursors could diborate alkenes at room temperature." The reactions proceed smoothly to give 1,2-diborylaIkanes in high yield, and the catalysts were compatible with common functional groups. Further developments in the area by Baker showed that [Pt(COD)Cl2] could efficiently activate B2cat2 and promote the diboration of terminal alkenes, vinylarenes, alkynes, and aldimines (Scheme 9). The last example was a great advance because it represented the first direct approach toward a-aminoboronate esters. 

Scheme 9 Diboration of aldimines with B2cat2 activated by [PtfCODlChl complex.

Mann G, John KD, Baker RT. Platinum catalyzed diboration using a commercially available catalyst diboration of aldimines to a-aminoboronate esters. Org Lett. 

---