Platinum(0)-Catalyzed Diboration of Alkynes with Tetrakis(alkoxo)diborons:  An Efficient and Convenient Approach to cis-Bis(boryl)alkenes

Abstract

Tetrakis(methoxo)- or bis(pinacolato)diboron [(RO)2BB(OR)2; (RO)2 = (MeO)2 (4a) and Me4C2O2 (1)] added to both terminal and internal alkynes in the presence of a catalytic amount of Pt(PPh3)4 to provide stereodefined cis-bis(boryl)alkenes (3) in excellent yields. Because reagents and reaction conditions were sufficiently mild, the procedure was readily extended to various functionalized alkynes. Mechanistic study revealed that the oxidative addition of bis(pinacolato)diboron (1) to Pt(PPh3)4 generates cis-Pt(BO2C2Me4)2(PPh3)2 (5), whose structure was fully characterized by multinuclear NMR spectroscopies as well as single-crystal X-ray diffraction analysis. Complex 5 exhibited high reactivity for insertion to the alkyne giving 3 in high yields, thus implying that the oxidative addition of the B−B bond to a Pt(0) complex is an initial step in the platinum(0)-catalyzed diboration of alkynes.

Bis(pinacolato)diboron

“…(A) In the presence of a platinum(0) catalyst, 1 undergoes addition reaction to alkynes to give exclusive cis-diborylated alkenes. 2,9 This reaction works very well on both terminal and internal alkynes. It also tolerates various functional groups in the side chain of R 1 and R 2 , such as epoxy, cyano, and carbonyl groups.…”

(μ2-Pinacolato-O,O')-bis(pinacolato-O,O')diboron

“…The compound B2pin2 is of interest with regard to the recently developed metalcatalysed diboration of alkynes (Ishiyama, Matsuda, Miyaura & Suzuki, 1993;Iverson & Smith, 1995Ishiyama et al, 1996;Lesley et al, 1996) and alkenes (Baker, Nguyen, Marder & Westcott, 1995) and the palladium-catalysed synthesis of (aryl)B(pin) compounds (Ishiyama, Murata & Miyaura, 1995). It appears that B2pin3 is also formed in reactions of pinacol with BH3.thf or BC13 (Herberich & Fischer, 1996).…”

Experimental and DFT studies on poly[octa-μ3-acesulfamato-O,O:N,O′;O′,N:O,O-tetraaquatetrabarium(II)] complex

“…Based on facile oxidative addition of B-Br and B-I bonds to Pt(0) centres [6], we became interested in the reactivity of diboranes(4) Br 2 B 2 R 2 (R = NMe 2 , Mes) towards low-valent phosphine platinum complexes. We have now successfully accomplished the synthesis of two different types of diboranyl (4) 2 Pt(Br){B(Mes)B(Mes)Br}], which features a dative bond from the platinum to the second boron atom, resulting in a distorted square-pyramidal geometry of the platinum centre [7]. In course of this reaction the released phosphine PEt 3 reacts with one equivalent of diborane (4) , formally a product of phosphine-induced 1,2-rearrangement of mesityl and bromine ligands [8].…”

“…Until recently the diborane component of diborane-diyl bridged ansa-complexes has been limited to the amino-substituted B(NMe 2 )-B(NMe 2 Acesulfame has been used as a non-caloric artificial sweetener since 1988 [1]. Its coordination properties are important because acesulfame has potential donor atoms which can form coordination bonds with metal ions [2].…”

“…Its coordination properties are important because acesulfame has potential donor atoms which can form coordination bonds with metal ions [2].…”