Enantioselective Synthesis of Hydroxy-Substituted DBN-Type Amidines as Potential Chiral Catalysts

Diastereoselective access to hexahydro- and octahydrofuro[f]indolizines analogues of phenanthro[f]indolizidines alkaloids

“…We focused our attention on the reduction of the chiral alcohol and/or the lactam carbonyl to the corresponding alkanes 4a and 4b. These tertiary amine bases are able to activate electrophiles through hydrogen bonding, which should have an influence during the phase differentiation 14 and consequently make them promising candidates as catalysts in catalytic asymmetric synthesis. Herein, we report our findings in this area starting from enantiopure alcohols 2a and 2b.…”

Amidines in Organic Synthesis

“…g-Lactam, which is derived from pyroglutamic acid by reduction, protection of the hydroxy group and conjugate addition to acrylonitrile, is subjected to a similar synthetic route to afford a desired amidine [15] (Scheme 3.16). Intermolecular hydrogen bonding between hydrogen on the hydroxy group and imino nitrogen was observed by X-ray crystallographic analysis.…”

“…Near the same time, a mannose-based amidine 6 was synthesized as a potential mannosidase inhibitor, but not a chiral auxiliary [14]. Three enantiopure hydroxyl substituted amidines 7 of the DBN-type were synthesized from 5-(phenylsulfonyl)pyrroridine-2-one by an oxazaborolidine-catalysed reductive desymmetrization of meso-imide followed by functionalization through N-acyliminium ion [15] (Figure 3.3 Numerous applications have been found for the uses of imidazole derivatives as ionic liquids and N-heterocyclic carbenes and their use in organic chemistry has been well discussed in books or reviews. Thus, in this chapter, the use of non-heteroaromatic amidine compounds as functional tools in asymmetric synthesis and the related chemistry after presentation of the preparation method of amidines will mainly be discussed.…”

A Highly Enantioselective and General Conjugate Addition of Thiols to Cyclic Enones with an Organic Catalyst This work was financially supported by National Institutes of Health (GM-61591), Research Corporation (RI-0311), and the Harcourt General Charitable Foundation.

“…[2±6] Under classical conditions, organohalides react with sodium to give mainly Wurtz coupling products. [7,8] Moreover, alkylsodium compounds show poor stability, especially in ethereal solvents. [9,10] As a consequence, in spite of the low cost of metallic sodium and the sometimes demonstrated interesting reactivity, [11] alkylsodium compounds have not been considered so far as valuable organometallic reagents in organic synthesis.…”