Selective Isomerization–Hydroformylation Sequence: A Strategy to Valuable α‑Methyl-Branched Aldehydes from Terminal Olefins

For the first time, an original selective isomerization-hydroformylation sequence to convert terminal olefins bearing an anionic moiety to α-methyl-branched aldehydes with unprecedented selectivities is reported. This opens up new synthetic avenues to these valuable building blocks from inexpensive and bioavailable substrates. The catalytic system involves a suitable selective monoisomerization catalyst and a selective supramolecular catalyst that preorganizes a substrate molecule prior to the hydroformylation reaction via hydrogen bonding. In principle, the strategy can be extended to other classes of substrates, providing suitable catalysts for the hydroformylation of internal alkenes

Mono‑, Di‑, and Triborylphosphine Analogues of Triarylphosphines

Diazaborinylphosphines based on the 1,8-diaminonaphthylboronamide heterocycle are prepared by a chlorosilane-elimination reaction, and their structural and bonding properties are compared to those of PPh₃. The precursor chloroborane ClB­{1,8-(NH)₂C₁₀H₆} (<b>I</b>) is fully characterized including its crystal structure, which features intermolecular π–π stacking, B···N interactions, and N–H···Cl hydrogen bonding. Treatment of <b>I</b> with Ph_3–<i>n</i>P­(SiMe₃)_<i>n</i> gave the corresponding Ph_3–<i>n</i>P­(B­{1,8-(NH)₂C₁₀H₆})_<i>n</i>, {<b>L</b>_<b>1</b> (<i>n</i> = 1), <b>L</b>_<b>2</b> (<i>n</i> = 2), and <b>L</b>_<b>3</b> (<i>n</i> = 3)}. The crystal structures of <b>L</b>_{<b>1</b>–<b>3</b>} reveal an increase in the planarity at P as a function of <i>n</i>, and the steric bulk of the diazaborinyl substituent B­{1,8-(NH)₂C₁₀H₆} is similar to that of a phenyl. Nucleus-independent chemical shift calculations were carried out that suggest that the 14 π-electron diazaborinyl substituent can be described as aromatic overall, though the BN₂-containing ring is slightly antiaromatic. The complexes <i>cis-</i>[Mo­(<b>L</b>_{<b>1</b>–<b>3</b>})₂(CO)₄] (<b>1</b>–<b>3</b>) are prepared from [Mo­(nbd)­(CO)₄] (nbd = norbornadiene) and <b>L</b>_{<b>1</b>–<b>3</b>}. From the position of the ν­(CO) (<i>A</i>₁) band in the IR spectra of <b>1</b>–<b>3</b>, it is deduced that the diazaborinyl substituent has a donating capacity similar to an alkyl group