Zinc hydride catalyzed hydroboration of esters.

The conjugated bis-guanidinate (CBG)-supported zinc hydride {LZnH}; L = {(ArHN)(ArN)-CN-C(NAr)(NHAr); Ar = 2,6-Et-CH} (I) is utilized as a catalyst for the hydroboration of esters with pinacolborane (HBpin) under mild reaction conditions. Various aryl and alkyl substrates containing electron-donating, withdrawing, and cyclic groups of esters are effectively converted into alkoxy boronate esters as products upon hydroboration. Furthermore, stoichiometric experiments have been performed to understand the plausible reaction mechanism for the hydroboration of esters.

Synthesis of low oxidation state zinc(I) complexes and their catalytic studies in the dehydroborylation of terminal alkynes.

A new example of a structurally characterized conjugated bis-guanidinate (CBG) supported zinc(I) dimer, , LZnZnL (3) (L = {(ArNH)(ArN)-CN-C(NAr)(NHAr)}; Ar = 2,6-Et-CH) with a Zn-Zn bond is reported. Moreover, homoleptic (3) and heteroleptic (Cp*ZnZnL, 2, (Cp* = 1,2,3,4,5-pentamethyl cyclopentadienide)) zinc(I) dimers are used as precatalysts in the dehydroborylation of a wide array of terminal alkynes. Furthermore, the active catalyst, CBG zinc acetylide (LZn-CC-Ph-4-Me), (5), is isolated which is confirmed by X-ray crystal structure analysis.