0000000000319649
AUTHOR
Antonio Simon Fuentes
New Strategies for the Synthesis of Fluorinated Vinylogous Amidines and β-Enamino Ketones
Reaction of fluorinated imidoyl chlorides 3 with ketimines 1a provides fluorinated 1,3-diimines, which were exclusively isolated as vinylogous amidine tautomers 2beta, with good yields. Fluorinated beta-enamino ketones 4 are obtained by regioselective hydrolysis of 2. Complementary methods for the synthesis of regioisomeric beta-enamino ketones 4 and 5 are also reported. These methods include the reaction of azaenolates of ketimines with fluorinated esters 6 and reactions of ketone enolates with fluorinated imidoyl chlorides 3. The behavior of these systems in hydrolysis reactions was also tested.
ChemInform Abstract: New Strategy for the Stereoselective Synthesis of Fluorinated β-Amino Acids.
Racemic and chiral nonracemic α-substituted and α-unsubstituted β-fluoroalkyl β-amino acid derivatives 6 and 9 have been synthesized in two steps starting from fluorinated imidoyl chlorides 1 and ester enolates. This approach is based on the chemical reduction of previously obtained γ-fluorinated β-enamino esters 4 by using ZnI2/NaBH4 in a nonchelated aprotic medium (dry CH2Cl2) as the reducing agent. A metal-chelated six-membered model has been suggested to explain the stereochemical outcome of the reduction reaction. The process takes place with high yields and with moderate to good diastereoselectivity. The best results related to diastereoselective reduction of chiral β-enamino esters 4…
Diastereoselective synthesis of fluorinated, seven-membered beta-amino acid derivatives via ring-closing metathesis.
[reaction: see text] Cis and trans seven-membered gamma,gamma-difluorinated beta-amino acid derivatives (III) have been prepared with a sequence that starts with imidoyl halides (I), which are condensed with suitable ester enolates to give intermediates (II). These, in turn, can be cyclized by means of a ring-closing olefin metathesis reaction and the product stereoselectively reduced to yield compounds (III) in good overall yields.
ChemInform Abstract: Synthesis and Reactivity of New β-Enamino Acid Derivatives: A Simple and General Approach to β-Enamino Esters and Thioesters.
A new strategy has been developed for the synthesis of several β-enamino acid derivatives. N,N‘-Carbonyldiimidazole has been used as C-acylating agent of methyl ketimines, providing a direct and simple route to new β-enamino carbonyl imidazole derivatives 2. These derivatives 2 were cleanly and efficiently transformed into β-enamino esters 4 (X = O) and thioesters 4 (X = S) by reaction with a great variety of alcohols and thiols, including tertiary ones. Alternative and complementary routes to compounds 4 were also investigated. In addition, β-keto esters 6 have been obtained by mild acid hydrolysis of β-enamino esters 4.
New Strategy for the Stereoselective Synthesis of Fluorinated β-Amino Acids
Racemic and chiral nonracemic alpha-substituted and alpha-unsubstituted beta-fluoroalkyl beta-amino acid derivatives 6 and 9 have been synthesized in two steps starting from fluorinated imidoyl chlorides 1 and ester enolates. This approach is based on the chemical reduction of previously obtained gamma-fluorinated beta-enamino esters 4 by using ZnI(2)/NaBH(4) in a nonchelated aprotic medium (dry CH(2)Cl(2)) as the reducing agent. A metal-chelated six-membered model has been suggested to explain the stereochemical outcome of the reduction reaction. The process takes place with high yields and with moderate to good diastereoselectivity. The best results related to diastereoselective reduction…
(−)-(4R,5R)-4,5-Bis[hydroxy(diphenyl)methyl]-2,2-dimethyl-1,3-dioxolane
[93379-48-7] C31H30O4 (MW 466.57) InChI = 1S/C31H30O4/c1-29(2)34-27(30(32,23-15-7-3-8-16-23)24-17-9-4-10-18-24)28(35-29)31(33,25-19-11-5-12-20-25)26-21-13-6-14-22-26/h3-22,27-28,32-33H,1-2H3/t27-,28-/m1/s1 InChIKey = OWVIRVJQDVCGQX-VSGBNLITSA-N (chiral shift reagent; chiral host in inclusion compounds; chiral reagent; chiral ligand for asymmetric catalysis) Alternate Name: TADDOL. Physical Data: mp: 190–192 °C1a; 195–196.5 °C1b; 192–193 °C;1c,e 193.5–195 °C;1d [α]RTd=−68.5 °(c = 1, CH3Cl);1a [α]d = −60.6 °(c = 1, CH3Cl);1b [α]20d = −67 ° (c = 1, CH3Cl);1c [α]20d = −65.1° (c = 1, CH3Cl);1d [α]20d = −64.6°(c = 1, CH3Cl)1e Solubility: soluble in toluene, cyclohexane, dichloromethane and tetra…
Synthesis and Reactivity of New β-Enamino Acid Derivatives: A Simple and General Approach to β-Enamino Esters and Thioesters
A new strategy has been developed for the synthesis of several β-enamino acid derivatives. N,N‘-Carbonyldiimidazole has been used as C-acylating agent of methyl ketimines, providing a direct and simple route to new β-enamino carbonyl imidazole derivatives 2. These derivatives 2 were cleanly and efficiently transformed into β-enamino esters 4 (X = O) and thioesters 4 (X = S) by reaction with a great variety of alcohols and thiols, including tertiary ones. Alternative and complementary routes to compounds 4 were also investigated. In addition, β-keto esters 6 have been obtained by mild acid hydrolysis of β-enamino esters 4.