A new class of phosphabarrelene-rhodium catalysts is described which allows for the first time hydroformylation of internal alkenes with very high activity and which proceeds essentially free of alkene isomerization.

Despite significant research efforts in the past, one of the remaining problems to be solved in industrially important hydroformylation is the chemoselective low-pressure hydroformylation of internal alkenes. We report here on a new class of phosphabarrelene/rhodium catalysts 2 that display very high activity towards hydroformylation of internal alkenes with an unusually low tendency towards alkene isomerization. Preparation of new phosphabarrelene ligands, studies of their coordination properties, as well as results obtained in the rhodium-catalyzed hydroformylation of cyclic and acyclic internal alkenes are reported.

C h i r a l P h o s p h a b a r r e l e n e L i g a n d s i n R h o d i u m -C a t a l y z e d A s y m m e t r i c H y d r o g e n a t i o n Abstract: The first chiral and enantiomerically pure monodentate and bidentate phosphabarrelene ligands have been prepared and their potential in rhodium-catalyzed asymmetric hydrogenation has been evaluated.

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Organophosphorus Compounds, 511). – Phosphatriafulvenes – Phosphaalkenes with Inverse Electron Density2) Peterson olefination of the sterically hindered cyclopropenones 1 with the lithium phosphides 2 yields the so far unknown phophatriafulvenes 3 and 4, which possess inverse electron densities. They are characterized by transition metal complex formation (→7, 8). Acylation of 3a with the carboxylic acid chlorides 11 leads to a great variety of P‐acylphosphatriafulvenes 13a‐s. They partly dimerize under formation of the 1,3‐diphosphacyclobutanes 13 ⇌ 14.