Synthesis of Chiral Bicyclic Guanidinium Salts using Di(imidazole-1-yl)methanimine.

A detailed account of the synthesis of chiral bicyclic guanidinium salts is presented. This work represents the first systematic investigation of an approach toward the challenging target molecules via a key guanylation step employing di(imidazole-1-yl)methanimine (6) followed by a two-fold cyclization, which resulted in guanidinium salts 8 and 10. Factors governing the regioselectivity of the final cyclization step are discussed based on further data obtained in the course of the attempted syntheses of two additional bicyclic guanidinium salts.

Synthesis of highly substituted oxetanes via [2+2] cycloaddition reactions of allenoates catalyzed by a guanidine Lewis base.

The first synthesis of highly substituted 3-alkyl-oxetan-2-ylidenes from allenoates was developed by using the bicyclic guanidine 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) as an exceptionally active nitrogen Lewis base catalyst.

Reversible generation of metastable enols in the 1,4-addition of thioacetic acid to α,β-unsaturated carbonyl compounds.

Addition of thioacetic acid to reactive α,β-unsaturated carbonyl compounds like acrolein or crotonaldehyde in acetone-d(6) generates metastable (E)- and (Z)-1-alkenols, which tautomerize slowly at ambient temperature. The 1,4-addition of thioacetic acid and crotonaldehyde to (Z)-3-(acetylsulfanyl)-1-propen-1-ol is reversible with K(eq) = 5.5 ± 0.