Enolboration. 4. An examination of the effect of the leaving group (X) on the stereoselective enolboration of ketones with various R2BX/triethylamine. New reagents for the selective generation of either Z or E enol borinates from representative ketones

Capturing HBCy2: Using N,O‐Chelated Complexes of Rhodium(I) and Iridium(I) for Chemoselective Hydroboration

“…[13] Ring expansion of the parent fourmembered metallacycles 3 and 4 is also evidenced by ac hange in the 31 P{ 1 H} NMR chemical shift to d = 22.1 ppm ( 2 J Rh,P = 4.5 Hz; Dd = 9.1) for 7 and d = 34.3 ppm (Dd = 6.6) for 8. 11 B{ 1 H} NMR spectroscopy additionally provided one broad signal attributable to an oxygen-stabilized sp 3 -hybridized boron atom at d = 13.0 ppm (w 1/2 = 573 Hz; Dd = À46.2; d = 59.2 for free HBCy 2 ) [14] for 7 and d = 14.6 ppm (w 1/2 = 670 Hz; Dd = À44.6) for 8.AnEIMSexperiment also showed as ignal at m/z 645 (7)a nd 735 (8)w ith the correct isotope pattern, though [MÀHBCy 2 ] + was identified as the base peak, thus highlighting the weak degree of stabilization provided to the borane by the phosphoramidate fragment in the gas phase.Unexpectedly,treatment of the sulfur analogues 5 or 6 with HBCy 2 (1 equiv) provided no reaction, as observable by 1 HNMR spectroscopy,t hus highlighting the importance of the P=O···B interaction.…”

Electrophilic Cyanation of Boron Enolates: Efficient Access to Various β‐Ketonitrile Derivatives

“…[25] Ab rief screening of solvents revealed that the use of Et 2 Ow as suitable for this system. [25] Ab rief screening of solvents revealed that the use of Et 2 Ow as suitable for this system.…”

Regiospecific, Enantiospecific Total Synthesis of C-19 Methyl Substituted Sarpagine Alkaloids Dihydroperaksine-17-al and Dihydroperaksine

“…22 I-B(Cy) 2 is also a highly stereoselective reagent for the enolboration of esters 23 and tertiary amides. 24 If all other parameters are kept the same, the inability of B-I-9-BBN to drive the haloboration reaction to completion was felt to be due to the rigid skeleton of the bicyclo ring of B-I-9-BBN as a major factor.…”