Molecular Design for a Novel Organotin Hydride and Ferric Chloride Mediated Michael Addition of Dicarboxylic Acid Esters to alpha,beta-Unsaturated Ketones

Molecular Design for a Novel Organotin Hydride Introduction The history of organotin hydride began in the year 1922 with the synthesis of trimethyltin hydride, Me3SnH, by Kraus and Greer. Since then organotin hydride has evolved multi-dimensionally, and has achieved recognition worldwide as a credible reagent in synthetic organic chemistry. There are several ways of preparation of organotin hydrides, but the most convenient one is reducing the corresponding tin halide by employing a complex metal hydride such as LiAlH4, NaBH4, R2AlH or B2H6. Organotin hydrides are versatile reagents. They can react at the hydrogen centre with electrphiles, nucleophiles, or free radicals. All the processes are important in organic synthesis, but the recent chemistry of the hydrides has been dominated by the radical reactions which provide important procedures in synthetic organic chemistry. Some well appreciated reaction of organotin hydrides are addition reaction to multiple bonds, reactions with protic acids and bases, hydrostannolysis of organic halides, etc. Simple trialkyltin hydrides are marred by separation, toxicity and disposal problems. These problems prompted chemists to look for ways out and the continuing saga of search for newer pastures included modification in the workup procedures, using catalytic amount of tin hydride or its precursor with stoichiometric amount of another hydride, using fluorous tin hydrides, water soluble tin hydrides, and polymer supported tin hydrides. In the past nine decades of the history, organotin hydrides have evolved from simple versions such as trialkyltin hydrides to versions which are much more complex but do have fascinating properties. Asymmetric synthesis is a key component of today's chemistry. To make organotin hydrides compatible in such synthesis, chiral organotin hydrides are being designed and developed to achieve enhanced enantioselectivity. Chiral organotin hydrides can serve as enantioselective reducing agents under free radical environment. Reagents which are chiral solely at the tin tend to undergo ready racemisation, and so most of the chiral tin halides and hydrides, which have been evaluated to date for asymmetric synthesis, have made use of chiral ligands on the tin. The idea of creating an organotin hydride with structure I.1 was conceived based on the fact that the molecule without tin-nitrogen coordination lacks steric rigidity and hence directional property in its reactivity. It is expected that in a.