Ketones diboration

Aromatische Aldehyde und Ketone lassen sich auch durch Dibor an unter elektrophiler Katalyse von Bortrifluorid-Atherat zu Kohlenwasserstoffen reduzieren8. Die Methode ist z.B. besonders zur Herstellung von Benzyl-cyclopropanen geeignet, die auf andere Weise nur schlecht zuganglich sind9. 

Diboration of a,/ -unsaturated ketones is promoted by platinum(O) complexes. Reaction of 4-phenyl-3-buten-2-one with bis(pinacolato)diboron in the presence of a platinum catalyst affords a boryl-substituted (Z)-boron enolate, that is, a 1,4-diboration product, in high yield with high stereoselectivity (Scheme 8). The isolated boron enolate is easily hydrolyzed by exposure to water, giving / -boryl ketones in high yields.66 Similar diboration of a,/ -unsaturated ketones has also been achieved with Pt(bian)(dmfu) (bian = bis(phenylimino)acenaphthene, dmfu = dimethyl fumarate).67 Although the... 

The catalytic asymmetric diboration of allenes provides a-substituted 2-boronyl allylic boronates of type 25 (see Eq. 32). One of them, 91, adds to ben-zaldehyde, albeit with a slight erosion of stereoselectivity (Eq. 65). The major P-hydroxy ketone stereoisomer, isolated after an oxidative work-up, originates from the putative chairlike transition structure 92. 

Diborination of ot, (3-unsaturated ketones has been reported.142 The diboration of enones with 274 gives 1,4-addition products 275-280 in the presence of a platinum(O) catalyst such as Pt(C2H4)(PPh3)2... 

The B2pin2 activation by ds-[Pt(r -CH2=CH2)(PPh3)2] was also found to be an effective catalyst precursor for the 1,4-diboration of a,P-unsaturated ketones at 80 °C for 12 h (Scheme 11), while [Pt(PPh3)4] as catalyst precursor required 20 h at 110 °C to add B2pin2 to the same activated olefins. A second generation of platinum system... 

---