Novel C1-Bridged Bisboronate Derivatives by Insertion of Diazoalkanes into Bis(pinacolato)diborane(4)

Abstract

The insertion reaction of bis(pinacolato)diborane(4) [(Me4C2O2)BB(O2C2Me4), 1] with various diazoalkanes provided novel representatives of a new class of substituted C1-bridged bis(pinacolato)diborane(4) derivatives 5a, 5b, 5c, and 5d in a range of 75−78% isolated yields. The reaction was efficiently catalyzed by Pt(PPh3)4 in toluene at 110 °C. Single-crystal X-ray diffraction, GCMS, and NMR multinuclear spectroscopies fully confirmed the structure and configuration of the new compounds. Crystals of 5a and 5c are centrosymmetric, while those of 5d are chiral. 5b crystallized with a somewhat unusual Fdd2 space symmetry. While its crystals are noncentrosymmetric, they contain mirror-related species. The degree of puckering of the five-membered C2O2B rings, as well as the dihedral angles between the mean planes of these rings, vary from one compound to another and to some extent from one ring to another within the same compound.

Unexpected Generation of Diastereomers by Double Diboration of a Dialkyne

“…Along with hydroboration, [1][2][3][4] transition-metalcatalyzed diboration [5] has become useful for the functionalization of unsaturated organic compounds. [6,7] This reaction is widely applicable to substrates such as alkynes [8,9] arynes, [10] alkenes, [11][12][13] carbenoids, [14,15] as well as diazo [16] and carbonyl compounds. [17][18][19][20] Although bis(catecholato)diborane(4) and bis(pinacolato)diborane(4) represent by far the most commonly employed diborane(4) species, the reaction is not restricted to their use.…”

Pd‐Catalyzed Negishi Cross‐Coupling of Vinyl Bromides with Diborylmethylzinc Chloride

“…In prior studies, such compounds have been prepared by the transition‐metal‐free insertion of B 2 pin 2 into N ‐tosylhydrazone, 3b by the metal–catalyzed alkene isomerization of gem ‐diborylalkanes containing an alkene moiety in the alkyl substituents, 4 or 1,4‐diboration of dienylboronate ester 2c . More recently, transition‐metal‐catalyzed cross‐coupling approaches have also been disclosed (Scheme 1(a)).…”

Uncommon carbene insertion reactions

“…Srebnik et al 75 reported a Pt-catalysed B–B bond insertion reaction of B 2 pin 2 and diazomethane or aryl-stabilized diazo compounds under thermal conditions, affording various stable gem -diborates in good yields ( Scheme 19a ). Kingsbury et al 76 extended the scope of this reaction to dialkyl-substituted diazo compounds ( Scheme 19b ).…”