CO2 and Sn(II) adducts of N-heterocyclic carbenes as delayed-action catalysts for polyurethane synthesis.

Catalytic rivals: Both CO(2)-protected tetrahydropyrimidin-2-ylidene-based N-heterocyclic carbenes (NHCs) and Sn(II)-1,3-dimesitylimidazol-2-ylidene, as well as Sn(II)-1,3-dimesitylimidazolin-2-ylidene complexes (example displayed), have been identified as truly latent catalysts for polyurethane (PUR) synthesis rivaling all existing systems both in activity and latency.A series of CO(2)-protected pyrimidin-2-ylidenes as well as 1,3-dimesitylimidazol-2-ylidene and dimesitylimidazolin-2-ylidene complexes of Sn(II) have been prepared. Selected single-crystal X-ray structures are reported. The new compounds were investigated for their catalytic behavior in polyurethane (PUR) synthesis. All compounds investigated showed excellent catalytic activity, rivaling the industrially most relevant catalyst dibutyltin dilaurate. Even more important, all compounds displayed pronounced latent behavior, in selected cases rivaling and exceeding the industrially relevant latent catalyst phenylmercury neodecanoate both in terms of latency and catalytic activity. This allows for creating one-component PUR systems with improved pot lifetimes. Pseudo-second-order kinetics were found for both CO(2)-protected tetrahyropyrimidin-2-ylidenes and for [SnCl(2)(1,3-dimesityldihydroimidazol-2-ylidene)], indicating a fast pre-catalyst decomposition prior to polyurethane formation. 1,3-Di(2-propyl)tetrahydropyrimidin-2-ylidene was additionally found to be active in the cyclotrimerization of various isocyanates, offering access to a broad variability in polymer structure, that is, creating both urethane and isocyanurate moieties within the same polymer.

Tandem hydroformylation/Fischer indole synthesis: a novel and convenient approach to indoles from olefins.

[reaction: see text] A novel one-pot synthesis of indole systems via tandem hydroformylation/Fischer indole synthesis starting from olefins and arylhydrazines is described. This tandem procedure leads directly to 3-substituted indoles if unsubstituted phenylhydrazine is used and to 3,5- respectively 3,7-disubstituted indoles if para- or ortho-substituted arylhydrazines are used.

2,3-Disubstituted indoles from olefins and hydrazines via tandem hydroformylation-Fischer indole synthesis and skeletal rearrangement.

The tandem hydroformylation-Fischer indolisation protocol is used in the synthesis of 2,3-disubstituted indoles. After hydroformylation of selected olefins to form alpha-branched aldehydes in a one-pot procedure these are condensed with phenylhydrazine to give hydrazones. Upon acid-promoted [3,3]-sigmatropic rearrangement indolenine intermediates with quaternary centres in the 3-position are formed, which, after selective Wagner-Meerwein-type rearrangement of one of the substituents from the 3- to the 2-position, lead to 2,3-disubstituted indoles. Several olefins, bearing substituents with various functional groups, as well as cyclic olefinic systems are investigated.

Synthesis of pharmacologically relevant indoles with amine side chains via tandem hydroformylation/Fischer indole synthesis.

[reaction: see text] The sequence of hydroformylation and Fischer indole synthesis starting from amino olefins and aryl hydrazines is described. In a convergent manner, the two units bearing pharmacologically relevant substituents are assembled in the final indolization step. This modular and diversity-oriented approach to tryptamines and homotryptamines can be conducted in water and allows synthesis of branched and nonbranched tryptamines as well as tryptamine-based pharmaceuticals such as the 5-HT1D agonist L 775 606.

Tandem hydroformylation-hydrazone formation-Fischer indole synthesis: a novel approach to tryptamides.

A novel one-pot synthesis of indole systems via tandem hydroformylation-hydrazone formation-Fischer indolization starting from allylic amides and aryl hydrazines is described. This tandem procedure directly leads to biologically interesting tryptamides and analogues.