Biomedical subjects

Sarah V Maifeld

Publications and source records attributed to Sarah V Maifeld.

5 recordsLinked to original sources

PubMed2005

Unusual Tandem alkynylation and trans-hydrosilylation to form oxasilacyclopentenes.

[reaction: see text] An unusual tandem reaction sequence to form oxasilacyclopentenes from carbonyls and alkynylsilanes in the presence of a catalytic amount of nucleophilic initiator has been discovered. The reaction proceeds readily at room temperature and is applicable to a wide variety of carbonyl substrates. While the reaction scope tolerates variable substitutions on the alkynylsilane, phenylacetylene-derived silane variants consistently achieved the best yield.

Aldehydes↗

PubMed2005

Group-selective ring-closing enyne metathesis.

The ring-closing metathesis (RCM) of dienynes represents a powerful methodology for the construction of mono- and bicyclic systems containing 1,3-diene functionality. Despite its synthetic potential, the utility of dienyne RCM is significantly reduced due to poor group selectivity. To circumvent this shortcoming, several strategies utilizing steric hindrance, electronic variation, relay metathesis and ring-closure kinetics have been implemented to exert control over the reaction pathways. This article highlights a variety of methods to achieve group-selective enyne RCM of dienynes.

Bridged Bicyclo Compounds↗

PubMed2004

Group-selective ring-closing enyne metathesis: concentration-dependent selectivity profile of alkynylsilyloxy-tethered dienynes.

Highly group-selective ring-closing metathesis of alkynylsilyloxy-tethered dienynes was achieved by using Grubbs first- and second-generation catalyst. The remarkable selectivity increase at higher concentration for differentiating between two alkene moieties in nearly identical steric and stereoelectronic environments is believed to be the result of a higher ring-closure rate for smaller-sized ring formation under rapid pre-equilibration of the two alkylidene species generated from either alkene moiety.

Alkenes↗

PubMed2004

Regio- and stereoselective enyne cross metathesis of silylated internal alkynes.

Cross metathesis between silylalkynes and various functionalized alkenes catalyzed by Grubbs carbene complex produced, in most cases, single regio- and stereoisomers of the resultant 1,3-dienes. Polar heteroatom substituents at the propargylic site are important for high reactivity and selectivity. An important mechanistic insight regarding the initiation event and the key propagating alkylidene in this reaction was obtained by employing a tandem cross metathesis ring-closing metathesis between a terminal alkene and a silylated alkyne possessing an alkene tether.

Alkenes↗

PubMed2004

Ruthenium-catalyzed silyl ether formation and enyne metathesis sequence: synthesis of siloxacycles from terminal alkenyl alcohols and alkynylsilanes.

Two consecutive ruthenium-catalyzed reactions have been achieved for the synthesis of siloxacycles from terminal alkenyl carbenols and alkynylsilanes. The metal-catalyzed dehydrogenative condensation between alcohols and silanes, generating molecular hydrogen as the only byproduct, allows for the subsequent enyne metathesis without isolating the intermediate silyl ethers. This system provides a streamlined synthesis of synthetically useful building blocks. [reaction: see text]

Alcohols↗