Biomedical subjects
Publications and source records attributed to Scott T Handy.
A new, base-stable, imidazolium room-temperature ionic liquid (RTIL) has been prepared and applied to the addition of Grignard reagents to carbonyl compounds. These reactions occur readily at ambient temperature to afford the alcohol products in good to excellent yield. The RTIL can be recycled and reused numerous times without any difficulty.
[reaction: see text] In an effort to develop a more concise route to differentially substituted pyrroles (such as that found in the lamellarins), a completely regioselective one-pot double Suzuki coupling has been discovered. The key feature is the use of a ligand-free palladium catalyst under optimized conditions, which results only in coupling of the C5 bromide. At this point, addition of a second boronic acid and a phosphine ligand enables coupling at the remaining C4 bromide.
A simple guide for predicting the order and site of coupling (Suzuki, Stille, Negishi, Sonogashira, etc.) in polyhaloheteroaromatics based upon the (1)H NMR chemical shift values of the parent non-halogenated heteroaromatics has been developed.
[structure: see text] Depending upon the reaction conditions, the reductive cyclization affords either the pinacol or normal hydrodimerization-type products. This selectivity is highly dependent upon the substitution at the beta-position of the enones.
[structure: see text] We report a homogeneous supported version of Koser's salt based on a room-temperature ionic liquid (RTIL) support. By altering the nature of the RTIL, a material was developed that was stable, recyclable, and readily separable from the tosyloxylated ketone products just by using variations in solvent polarity. A similar approach should be applicable to a wide range of supported catalysts and reagents.
The 2-position of imidazolium cations is known to be relatively acidic, leading to the useful Arduengo-type carbenes. At the same time, the acidity of this site can lead to undesired side reactions when using imidazolium-based ionic liquids as solvents. In this note, we describe the surprisingly facile deuterium exchange at this position and also the synthesis and exchange under modestly basic conditions (triethylamine) of a series of 2-methyl-substituted compounds.
A modular synthesis of the lamellarin family of natural products has been developed that is based on the application of three iterative halogenation/cross-coupling reaction sequences. The ability to halogenate the pyrrole core in a regioselective fashion, even in the presence of highly electron-rich aryl substituents, has been established. The compatibility of Suzuki coupling conditions with free alcohols and phenols in the boronic acids has been employed to reduce the number of protection/deprotection steps. Indeed, the presence of a free phenol on boronic acid 3 has been determined to be critical for the successful final coupling in route to lamellarin G trimethyl ether, since protected versions fail to undergo coupling.
[reaction: see text] Fructose has been used as the starting material for the preparation of a new class of room-temperature ionic liquids (RTILs). These liquids exhibit tunable solvent properties much like conventional imidazole-based RTILs. They have been applied as recyclable solvents for the Heck reaction of aryl iodides.