Neville D. Emslie

Intramolecular Baylis-Hillman Reaction: A Pathway to Substituted Coumarins

Abstract The acrylate ester of salicylaldehyde, in the presence of DABCO, affords a crystalline coumarin salt. Formation of this derivative confirms a vital intermediate in the mechanism of the reaction. Salicylaldehyde, suitably protected, reacts with methyl acrylate to afford a novel coumarin not unlike the vasodilator chromonar.

SOME MECHANISTIC AND SYNTHETIC ASPECTS OF THE DABCO CATALYSED REARRANGEMENT OF ALLYLIC ESTERS

Abstract Experimental evidences shows that the (DABCO) catalysed rearrangement of allylic esters proceed via a two path mechanism, rather than a single path, as has been previously proposed. The effectiveness of other catalysts as well as E : Z ratios for these DABCO catalysed reactions have also been determined.

Synthesis of 3-Hydroxy-2-Methylene Carbonyl Compounds - Effect of Catalyst and Substrate on Reaction Rate

Abstract 3-Hydroxyquinuclidine enhances the rate of formation of the title compounds whereas the acetylated derivative is a poor catalyst. A comparative study shows that methyl vinyl ketone is more reactive than methyl acrylate in the Baylis-Hillman reaction.

DABCO-Catalysed Dimerisation of Some α,β-Unsaturated Esters

Abstract Aerylate esters readily undergo the Baylis-Hillman reaction with aldehydes in the presence of DABCO. In the absence of aldehydes it has now been established that esters with good leaving groups undergo self condensation (Michael addition) to afford dimers in almost quantitative yield.

Synthesis, resolution and assignment of absolute configuration of 2-(α-hydroxy)aryl acrylate esters

Abstract (−)(R,R)-2-Amino-1-(4-nitrophenyl)propan-1,3-diol 3 has been used to resolve racemic 3-hydroxy-2-methylene-3-phenylpropanoic acid 1a . Conversion of the laevorotatory enantiomer into anti and syn methyl 3-hydroxy-2-methyl-3-phenylpropanoate, 2a and 2b respectively, was achieved with Pd/H 2 . Correlation of the specific rotations of 2a and 2b with isomers of known configuration established the absolute configuration of 4a as R. This was confirmed independently by X-ray crystallography.

Synthesis of Useful Intermediates from the Claisen-Rearrangement of α-Hydroxy Alkyl Acrylate Precursors

Abstract The synthesis of two synthetic intermediates 1 and 2, from alkyl-3-hydroxy-2-methylene butanoate via transformations involving Claisen rearrangements, is described

(-)-8-Phenylmenthyl Acrylate as Chiral Inducer in the Baylis-Hillman Reaction

Abstract 8-Phenylmenthol 1 is used as a chiral auxiliary in the Baylis-Hillman reaction using a range of aldehydes as substrate. Best results (70% d. e.) are obtained when the reaction is rapid, as is the case with trichloroacetaldehyde.

Necic acid synthons. Part 1. Total synthesis of integerrinecic acid

The synthesis of racemic integerrinecic acid from ethyl acrylate is described. Overall, five steps are involved. A key synthon in the synthesis, ethyl (2Z)-2-bromomethylbut-2-enoate, can undergo either allylic substitution or substitution with rearrangement, and opens the way for a ‘general’ synthesis to a range of necic acids.

1,2-Addition of Activated Vinyl Carbanions to α,β-Unsaturated Carbonyls

Abstract Methyl acrylate reacts with α,β-unsaturated aldehydes in the presence of a tertiary amine to afford 1,2-addition products.

A novel tetrahydrofuran derivative via a tertiary ketol-type rearrangement

Abstract Hexahydro-3a, 7a-dihydroxy-3,7,7-trimethyl-2-phenyl-4H-furo [3,2-c]pyran-4-one 6 has been obtained from the reaction between tetrahydro-4, 4-dimethyl-2-oxo-3-furanyl propanoate 4 , benzaldehyde and base. The product is the result of a modified benzilic acid rearrangement.