Access to Cyclic Amino Boronates via Rhodium-Catalyzed Functionalization of Alkyl MIDA Boronates

Abstract

Herein, we describe the rhodium-catalyzed C-H amination reaction of 1,2-boryl sulfamate esters derived from amphoteric α-boryl aldehydes. Depending on the substitution pattern of the boryl sulfamate ester, a diverse range of five- or six-membered ring heterocycles are accessible using this transformation. The highly chemoselective nature of the C-H functionalization reaction preserves the alkyl boronate functional group, which enables the synthesis of B-C-N and B-C-C-N motifs that are present in a number of hydrolase inhibitors.

gem‐Difluorination of Alkenyl N‐methyliminodiacetyl Boronates: Synthesis of α‐ and β‐Difluorinated Alkylborons

“…Based on these elegant works and the notion that electron-rich sp 3 -boron centers are capable of stabilizing acations by hyperconjugation, [14] we hypothesized that the use of substituted alkenyl MIDAb oronates in the hypervalent iodoarene mediated 1,1-difluorinative rearrangement could deliver ad ifluoromethylated organoboron by MIDA-boryl migration (Scheme 1c). Based on these elegant works and the notion that electron-rich sp 3 -boron centers are capable of stabilizing acations by hyperconjugation, [14] we hypothesized that the use of substituted alkenyl MIDAb oronates in the hypervalent iodoarene mediated 1,1-difluorinative rearrangement could deliver ad ifluoromethylated organoboron by MIDA-boryl migration (Scheme 1c).…”

“…It was found that the MIDA‐boryl group migrated in preference to hydride, alkyl, and aryl substituents (Scheme b). Based on these elegant works and the notion that electron‐rich sp 3 ‐boron centers are capable of stabilizing α‐cations by hyperconjugation, we hypothesized that the use of substituted alkenyl MIDA boronates in the hypervalent iodoarene mediated 1,1‐difluorinative rearrangement could deliver a difluoromethylated organoboron by MIDA‐boryl migration (Scheme c). Interestingly, an extensive literature review revealed that methods for the synthesis of β‐difluorinated alkylborons were largely unexplored .…”

Synthesis and Applications of β‐Aminoalkylboronic Acid Derivatives

“…Rh‐Catalyzed C−H amination of boryl sulfamates, as reported by Yudin and co‐workers, provides an effective method for the preparation of heterocyclic β‐aminoalkylboronates (Scheme 22). [63] When a MIDA boryl sulfamate bearing a benzyl substituent (R = Ph) is employed in this reaction, it results in a six‐membered β‐aminoalkylboronate product in a good yield (58%) with high diastereoselectivity (>20:1 dr). A notable drawback of this C−H amination arises with the use of alkyl‐substituted (R=alkyl) MIDA boryl sulfamates, which delivers the six‐membered β‐aminoalkylboronate products in only low to moderate yields with poor diastereoselectivity (1:1–4:1 dr), accompanied with 17–38% of five‐membered α‐aminoalkylboronate side products.…”

gem‐Difluorination of Alkenyl N‐methyliminodiacetyl Boronates: Synthesis of α‐ and β‐Difluorinated Alkylborons

“…Zuschriften me 1b). Based on these elegant works and the notion that electron-rich sp 3 -boron centers are capable of stabilizing acations by hyperconjugation, [14] we hypothesized that the use of substituted alkenyl MIDAb oronates in the hypervalent iodoarene mediated 1,1-difluorinative rearrangement could deliver ad ifluoromethylated organoboron by MIDA-boryl migration (Scheme 1c). Interestingly,a ne xtensive literature review revealed that methods for the synthesis of b-difluorinated alkylborons were largely unexplored.…”