Richard P. Polniaszek

Diastereoselective addition of organometallic reagents to chiral iminium ions: Synthesis of (S)-(+)-cryptostyline I.

Abstract Iminium ion 2c participates in stereoselective nucleophilic addition reactions with Grignard reagents. Analysis of the products from reaction of 5-hexenylmagnesium bromide with iminium ion 2a suggests that these reactions proceed by a polar (two electron) mechanism. The utility of this chemistry is demonstrated in a stereospecific synthesis of (S)-(+)-cryptostylina I.

Stereoselective reductions of chiral iminium ions

Abstract Chiral iminium ions derived from α-phenethylamine have been reduced stereoselectivey with NaBH4. Diastereoselection of the reduction ranged from 88:12 to 94:6. The sense of asymmetric induction has been unambiguously assigned by correlation of reduction products with S-(−)-salsolidine and S-(−)-nor-laudanosine.

Remarkable examples of double diastereodifferentiation: Application to the Eudistomin and Eudistomidin alkaloids

Abstract Nucleophilic addition of chiral enolates 1 and ent- 1 with chiral iminium ion 2a occur with total stereochemical control.

An Efficient Preparation of (S)-(-)-1-(2,6-Dichlorophenyl)ethylamine

Abstract (S)-(-)-1-(2,6-Dichlorophenyl)ethylamine has been prepared from (S)-α-phenethylamine in 2 steps in 44% overall yield.

Stereospecific Preparation of Transglycidic Esters

Abstract Trans-disubstituted glycidic esters have been prepared stereospecifically by reaction of the dicyclopentylboryl enolate of α-bromo-t-butylthioacetate with aromatic aldehydes.

Preparation of (2S∗, 5S∗) -2,5-Dibenzyl Phospholanic Acid

Abstract Phosphenium ion 1 underwent cheletropic cycloaddition with E-1-benzylbutadiene 2b to afford cyclic phosphonium salts 3b and 4b. In situ hydrolysis of the phosphonium salts produced phosphinamides 6a and 6b in a 3:1 ratio. Three chemical steps coverted phosphinamide 6a to the title compound 12b.