Transition-metal-promoted reactions of boron hydrides. 10. Rhodium-catalyzed syntheses of B-alkenylborazines

Recent Advances in Organic Synthesis Using Transition Metal-Catalyzed Hydroborations

“…Since this seminal discovery, a considerable amount of research by the groups of Evans [9][10][11][12][13][14], Burgess [15][16][17][18][19][20][21], Baker and Marder [21][22][23], Sneddon [24][25][26], Hayashi [27,28], Suzuki [29,30] and Merola [31] has focussed on investigating the mechanism and scope of these catalyzed hydroboration reactions. While several excellent reviews have already been published in this area [32][33][34][35][36][37][38], the goal of this paper is to summarize the important findings in this area and discuss the use of this reaction in organic synthesis.…”

The Development of Enantioselective Rhodium-Catalysed Hydroboration of Olefins

“…[45] Therefore, there have been considerable efforts to find alternative hydroborating agents. These include 4,4,6-trimethyl-1,3,2-dioxaborinane [6] (11) and pinacolborane [24,47,48,63 -65] (12), with emphasis on boron hydrides bearing boron -oxygen bonds, [39] as well as borazine [66,67] (13, Figure 1). Despite these endeavours, catecholborane (1) is still the most useful borane and rhodium complexes the most useful catalysts for catalytic hydroboration.…”

Hydroboration, Diboration, Silylboration, and Stannylboration

“…The high stability of the resulting products (pinacol esters of alkyl-or 1-alkenylboronates) to moisture and chromatography is also very convenient for organic chemists. Other borane reagents including 4,4,6-trimethyl-1,3,2-dioxaborinane (3) [14], oxazaborolidines (4) [15] , benzo-1,3,2-diazaborolane (5) [16], and borazine (8) [17] may also be used, but the scope of these reagents remains to be explored.…”

“…The steric effect of borane reagents also plays an important role in selectivity. Pinacolborane selectively adds to the terminal carbon because of its bulkiness (entries [17][18][19][20], which is in sharp contrast to the internal addition of catecholborane according to the electronic effect of the phenyl group. Although RhCl(PPh 3 ) 3 results in a complex mixture for styrene including regioisomers (9, 10) and a dehydrogenative coupling product PhCH=CHBpin (entry 17), other Rh(I), Ni(II), and Ir(I) catalysts reveal high terminal selectivity (entries 18-20) [33][34].…”

“…of Et 3 N. The β-hydrogen in the cis-product unexpectedly does not derive from the borane reagents because a deuterium label at the terminal carbon selectively migrates to the β-carbon (Scheme 1-5). A vinylidene complex (17) [45] generated by the oxidative addition of the terminal C-H bond to the catalyst is proposed as a key intermediate of the formal trans-hydroboration.…”