Asymmetric Syntheses of New Functionalized β-Amino Alcohols via Diastereoselective Addition of Organometallic Reagents onto Oxazolidines

Abstract

Diastereoselective reactions between (S)-phenylglycinol-derived oxazolidines and two unsaturated organolithium reagents afforded chiral beta-amino alcohols having vinyl and alkynylsilane moieties. When the same reactions were performed in the presence of titanium isopropoxide, a dramatic change of regioselectivity was observed, from the alpha- to the gamma-position, thus producing beta-amino alcohols with allyl or allenylsilane functions. A rationalization of the observed diastereoselectivity was suggested for each case.

Titanium Tetraisopropoxide

“…Thus, iodotrifluoromethane and oxazolidines undergo the addition of titanates generated from titanium tetraisopropoxide, the first allowing trifluoromethylation processes 59 and the latter establishing a method for the synthesis of asymmetric functionalized β-amino alcohols (eq 42). 60 Titanium tetraisopropoxide also promotes the palladiumcatalyzed allyl substitution of carbon nucleophiles to allyl acetates, and the obtained results compare favorably with the usually employed BSA/AcOK system. 61 On the other hand, titanium tetraisopropoxide can also act itself as an alkoxy nucleophile donor.…”

Mild Synthesis of β‐Amino‐α,α‐difluoro Ketones from Acylsilanes and Trifluoromethyltrimethylsilane in a One‐Pot Imino Aldol Reaction

“…[22] The acylsilanes 1 and 2 were synthesized by the method developed by Corey [23] and Brook [24] and their co-workers. Imines 3c, [25] 3d, [26] 3e, [27] 3f, [11b,28,29] and oxazolidine 3i [30] were prepared according to literature procedures.…”

Aliphatic aldehydes in the synthesis of carbo- and heterocycles. Part I. Synthesis of three-, four-, and five-membered rings

“…It should be noted that the charge on the C 2 atom originating from the carbonyl group changes to the opposite in going to dithio acetals 117, so that it can be alkylated through lithium derivative 118. This reaction opens the way for conversion of aldehydes into ketones 119 that are difficult to obtain by other methods [144][145][146][147] Chiral 1,3-oxazolidines derived from β-amino alcohols and aldehydes are important intermediates in numerous asymmetric syntheses [148][149][150][151][152][153][154][155][156][157]. Badiang and Aube [158] were the first to develop a procedure for the synthesis of 2-alkyl-4,5-dihydrooxazoles 120 from aldehydes 9d and 9e and β-hydroxyalkyl azides 121.…”