Novel high hydroxyl number and high functionality polyols were developed using thiol-ene reaction of castor oil with mercaptoethanol or mercaptanized castor oil with allyl alcohol (by photochemical reaction) and 2-hydroxyethyl acrylate (by Michael thiol-ene reaction). The polyols had OH numbers of 220-295 mg KOH/g and functionalities close to 6. Cast polyurethane resins were prepared with methylene diphenyl diisocyanate (MDI), dicyclohexylmethane-4,4'diisocyanate (HMDI) and m-xylylene diisocyanate (XDI). XDI gave rubbery to leathery polyurethanes with all three polyols, while MDI and HMDI gave amorphous glasses with good mechanical properties. Rigid polyurethane foams of good properties were made with MDI and three castor oil-based polyols.
We report full details of a method for 1,3-reductive transposition of α-alkoxy-α,β-unsaturated hydrazones to provide E-alkenes with high 1,4-stereocontrol between the two respective allylic stereocenters. The process couples a chelation-controlled reduction of the hydrazone with an in situ allylic strain controlled retro-ene reaction of an allyl diazene, i.e., an allylic diazene rearrangement. Such stereotriads are frequently observed motifs in natural products. We observed a fortuitous kinetic preference for the E-hydrazone geometry during the hydrazonation reaction, as only the E-isomers could undergo chelation-controlled reduction.
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