Trimethylamine-N-oxide TMANO

A combination of a metathesis and a Pauson-Khand reaction, which leads to tricyclic compounds starting from diene-ynes, has been described by Perez-Castells and colleagues [262]. Treatment of the Co-complex 6/3-86, obtained from the corresponding alkyne in 75 % yield, with 5 mol% of the Ru-catalyst 6/3-13 for 18 h, followed by addition of an N-oxide as trimethylamine-N-oxide (TMANO) or NMO as copromoters, gave 6/3-87 in 81% yield. 

Soderquist and Najafi [22] have reported the selective monoxidation of B-substituted derivatives of 9-BBN to afford in good yield the exclusive formation of 9-oxa-10-borabicyclo[3.3.2]decane products (Eq. 3.8 Table 3.6). The reaction proceeds smoothly using 1 equiv of anhydrous trimethylamine N-oxide (TMANO) in CHCl, at 0 °C. 

The terminal alkynes react with 2 equiv of 9-BBN and affords, quantitatively, the corresponding 1,1-diboraylalkanes. Soderquist has reported that this trialkyl-borane reacts with 1 equiv of benzaldehyde or 1-NaphCHO in 2 h at 25 °C, and quantitatively form B-ArCH20-9-BBN and B-alkenyl-9-BBN, exclusively with tram configuration [18]. The frans-B-alkenyl-9-BBN undergoes selective oxidation [18] with 1 equiv of anhydrous trimethylamine-N-oxide (TMANO) [19] and affords almost quantitatively the corresponding stable fraws-B-vinyl-9-oxa-10-borabicyclo[3.3.2]decane derivatives (traws-B-vinyl-OBBD). tram-B-Yinyl-OBBD derivatives are inert to atmospheric oxygen and are unreactive toward protonolysis (HOAc, 25 °C, 8 h) or insertion process (PhCHO, neat, 80 C, 6 h). The reaction sequence for the synthesis of fraws-B-vinyl-OBBD is outlined in Scheme 20.6 [18]. 

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