Synthesis of Tri‐ and Tetrasubstituted Alkenyl Boronates from Alkynes

Abstract

The synthesis of organoboron compounds have attracted the attention of the synthetic community. In particular, molecules with C(sp2)‐B bonds enable the transformation to new C−C or C‐heteroatom bonds by well‐established methodologies. Alkenyl boronates have the possibility for further conversion of the boron moiety or functionalization of the double bond. This review gives an overview on the recent methodologies for the selective preparation of the challenging highly substituted alkenyl boronates from alkynes.

How to Break the Law: trans‐Hydroboration and gem‐Hydroboration of Alkynes

“…Though not strictly falling into the scope of this short review, brief (but not comprehensive) reference is made to other transaddition reactions of boron-containing reagents to alkynes. [80,81] Arguably most notable in this context is trans-diboration; if followed by a (regio)selective mono-proto-deborylation, a net trans-hydroboration of the substrate is achieved, although at the expense of a valuable boron entity (Figure 19). [82] Better use of this substituent is made if trans-diboration is paired with an appropriate boron-mediated CÀ C coupling reaction.…”

Transition metal-free radicaltrans-hydroboration of alkynes with NHC-boranesviavisible-light photoredox catalysis

“…In general, most research has been focused on traditional transition-metal-catalyzed approaches. 3 Recently, radical alkyne hydroboration has emerged as a conceptually appealing and promising approach because it may offer regio- or stereoselectivities different from those of transition-metal-catalysis. However, this has rarely been explored.…”

Selective synthesis of boron-substituted enynesviaa one-pot diboration/protodeboration sequence

“…10 Thus, the selective and efficient synthesis of enynylboronates is a challenging synthetic task. In contrast to the well-established synthesis of alkenyl 11–13 or dienyl boronates, 14,15 the formation of enynylboronates is limited to a few examples.…”

“…10 Thus, the selective and efficient synthesis of enynylboronates is a challenging synthetic task. In contrast to the well-established synthesis of alkenyl [11][12][13] or dienyl boronates, 14,15 the formation of enynylboronates is limited to a few examples.Several different approaches, such as organocatalytic, 16 radical 17 and TM-catalyzed borylations, [18][19][20][21][22] were applied to access enynylboronates. However, the latter is the most developed.…”