Pattern recognition analysis in complex molecule synthesis and the preparation of iso-Diels-Alder motifs.

The identification of synthesizable substructural domains within more complex structural targets is of significant value in designing a workable plan of synthesis. We term this process "pattern recognition analysis" (PRA). In this paper we continued to build on the theme of PRA as a potential resource in retrosynthetic blueprints to reach highly challenging targets. The paper operates at two levels. First, there is provided a clear sense of definitions of categories by which patterns are related to hypothetical reaction types. Although the required reaction type may for the moment not exist, we believe that this method of analysis is likely to promote innovation that identifies unmet needs and opportunities to advance the cause of complex target synthesis. In addition, we describe reductions to practice in expanding the menu of achievable patterns. It is likely that the future value of PRA will be associated with its utility in leading the way to new and exploitable chemical innovation.

Rhodium-catalyzed redox allylation reactions of ketones.

Ketones react with allyl acetate to generate tertiary homoallylic alcohols in the presence of a rhodium catalyst and bis(pinacolato)diboron. A range of substrates, including aryl, alkyl and cyclic ketones react smoothly under these conditions. Diastereoselective allylation reactions of functionalized ketones such as pregnenolone acetate are also reported.

Oxazolidine synthesis by complementary stereospecific and stereoconvergent methods.

Complementary stereospecific and stereoconvergent reactions for enantioselective synthesis of 1,3-oxazolidines are reported. In the presence of a rhodium catalyst, reaction of enantioenriched butadiene monoxide with aryl imines is stereospecific (99% ee). Alternatively, the reaction of racemic butadiene monoxide, in the presence of a chiral palladium or nickel catalyst, provides an enantioselective synthesis of 1,3-oxazolidines (up to 94% ee). Synthesis of either the cis- or trans-1,3-oxazolidines is also accomplished under catalyst control.

Further Expansion of the trans-Diels-Alder Paradigm: Reductive Alkylation of α-Cyanoketones.

Reductive alkylation of Diels-Alder derived ring junction- α-cyanoketones provides a route to trans-fused bicyclic systems.

Palladium-catalyzed, one-pot, three-component synthesis of homoallylic amines from aldehydes, anisidine, and allyl trifluoroacetate.

An allylation reaction that generates homoallylic amines using allyl trifluoroacetate as a nucleophilic allylmetal precursor is reported. A palladium complex catalyzes two transformations in one pot: formation of allylsilane from allyl trifluoroacetate using hexamethyldisilane and subsequent imine allylation. A three-component reaction was developed where preformed imines were replaced with aldehydes and anisidine. Under these reaction conditions a variety of substrates, including electron-rich aromatic and aliphatic aldehydes, react smoothly to afford homoallylic amines.