Profiling the tuneable R-SMS-Phos structure in the rhodium(i)-catalyzed hydrogenation of olefins: the last stand?

Abstract

A diversified family of enantiopure P-stereogenic "R-SMS-Phos" {R-SMS-Phos = 1,2-bis[(o-RO-phenyl)(phenyl)phosphino]ethane} ligands wherein R = branched or heteroatom-substituted alkyl, aralkyl, silyl, acyl, sulfonyl, etc. was screened for the Rh(I)-catalyzed hydrogenation of a representative set of olefinic substrates. This systematic and detailed investigation revealed a marked beneficial impact on enantioselectivity and catalyst activity in comparison to Knowles' ultimate DiPAMP {DiPAMP = 1,2-bis[(o-anisyl)(phenyl)phosphino]ethane} design. Mutant ligands with highly enhanced properties possessing particular features wherein the DiPAMP structure is found embedded were identified.

Effect of biological degradation by termites on the flexural properties of pinewood residue/recycled high‐density polyethylene composites

“…Additionally, in agreement with related literature, the results of this study demonstrate that termites were able to mechanically deteriorate wood and plastics by the action of their mandibles 24 and that while searching for food, they penetrated and damaged both cellulolytic and noncellulolytic materials, breaking them apart. 9 As a result, their mechanical properties were affected.…”

“…Smooth and even rough surfaces are more likely to prevent it, but even the smallest cracks and crevices or ruffled surfaces and edges provide immediate access for their mandibles. 9 Hence, we believed it would be interesting to investigate the effects of this type of biotic attack on weathered and nonweathered WPCs, especially those intended for outdoor applications. Consequently, as part of a broad research project, we studied the availability of wood and plastic wastes generated in the Yucatan state (southeastern Mexico) to be used in the preparation of WPCs with potential applications as structural materials.…”

P-Stereogenic Phospholanes or Phosphorinanes fromo-Biarylylphosphines: Two Bridges Not Too Far

“…In our ongoing reasearch and development of ( P - ortho -substituted aryl)-borne ethane-bridged diphosphines following the latter methodology, we explored the synthesis of P - o -biarylyl congeners. The preparation of the basic enantiomeric 1,2-bis[( o -biphenylyl)(phenyl)phosphino]ethane diphosphine has been accomplished from its P -oxide derivative via a Cu-mediated dimerization .…”

Olefin Hydrogenation with Rigid Mono‐P‐stereogenic Diphosphines: A Flexible Rhodium Ring to Rule Them All?

“…Most importantly, the hydrogenation rates for MAC and AS were much higher with 1,2‐bis[(aryl)(phenyl)phosphino]ethanes [wherein aryl = o ‐RO‐Ph,6a,15 2,3‐(MeO) 2 ‐Ph, 2,3,4,5‐(MeO) 4 ‐Ph20] than with L1 – L4 , demonstrating a clear beneficial impact on the hydrogenation kinetics of the flexible CH 2 CH 2 backbone in such P , P , P′ , P′ ‐tetraaryl PCCP‐type bridged structure. However, the P ‐α‐Nap‐substituted analogue21 displayed much lower hydrogenation rates for MAC and AS compared with DiPAMP15 or 1,2‐bis[(methyl)(phenyl)phosphino]ethane17a (having comparable rates), and 1,2‐bis{[2,3‐(MeO) 2 ‐Ph](phenyl)phosphino}ethane,20 but gave the same level of enantioselectivities as with the latter, pointing here also to the unfavorable increase in the overall rigidity of the system.…”