Reaction Of Tert-butyl Research Articles

Stereoselectivity of Michael Addition of P(X)-H-Type Nucleophiles to Cyclohexen-1-ylphosphine Oxide: The Case of Base-Selective Transformation.

Michael addition of phosphorus nucleophiles to the unsymmetrically substituted tert-butyl(1,4-cyclohexadien-3-yl)phosphine oxide and its derivatives has been described. The addition proceeds with the formation of the mixture of two isomeric products with good yield and diastereoselectivity. The reaction of tert-butyl(cyclohexen-1-yl)methylphosphine oxide with phosphorus nucleophiles is base sensitive and might afford two epimers which differ at one chirality center. The absolute configuration of the products has been assigned on the basis of conformational and (1)H NMR analysis, and the mechanism of the reaction has been discussed. The Michael addition of phosphorus nucleophiles is postulated to proceed with or without consecutive epimerization of two α-carbanions.

Strong base- or acid-mediated chemoselectivity shifts in the synthesis of 2H-chromene or coumarin derivatives from common Baylis-Hillman adducts

Reaction of tert-butyl 3-(2-hydroxyphenyl)-2-methylenepropanoate esters with aqueous KOH provides convenient and chemoselective one-pot access to 2H-chromene-3-carboxylic acids, the overall transformation involving tandem conjugate addition, hydrolysis and elimination steps. The methodology complements the chemoselective, acid-catalysed route to 3-substituted coumarins from the same substrates by switching the regioselectivity of cyclisation.

Tert-Butyl N-[2-(N-isobutyl-4-meth-oxy-benzene-sulfonamido)-eth-yl]carbamate.

The title compound, C18H30N2O5S, was synthesized by the reaction of tert-butyl 2-(iso­butyl­amino)­ethyl­carbamate with p-meth­oxy­phenyl­sulfonyl chloride. In the mol­ecule, two intra­molecular C—H⋯O hydrogen bonds are observed. In the crystal, mol­ecules are linked by N—H⋯O hydrogen bonds involving the imino group N atom and the ester group O atom into chains running parallel to the b axis. The chains are further connected by C—H⋯O hydrogen bonds, forming layers parallel to the bc plane.

Synthesis of 9-Substituted Derivatives of tert-Butyl 6-(9h-Purin-6-Ylthio) Hexylcarbamate

We report herein the synthesis of series of 9-substituted derivatives of tert-butyl 6-(9H-purin-6-ylthio) hexylcarbamate by the reaction of tert-butyl 6-(9H-purin-6-ylthio) hexylcarbamate with different acid chlorides using triethylamine in Dichloromethane solvent.

Tautomerism in Quinoxalines Derived from the 1,4-Naphthoquinone Nucleus: Acid Mediated Synthesis, X-ray Molecular Structure of 5-Chlorobenzo[f]quinoxalin-6-ol and Density Functional Theory Calculations

The reaction of tert-butyl 2-(3-chloro-1,4-dioxo-1,4-dihydronaphthalen-2-ylamino) ethylcarbamate with CF3COOH/CH2Cl2 yields 5-chloro-3,4-dihydrobenzo[f]quinoxalin6(2H)-one which undergoes acid-promoted dehydrogenation in the presence of water to give novel 5-chlorobenzo[f]quinoxalin-6-ol. The molecular structure of 5-chlorobenzo[f]quinoxalin6-ol in the solid state, determined by an X-ray diffraction (XRD) study, and the solution data confirm that it exists as the enol-imine tautomer, both in the solid state and in solution, differently from 5-chloro-3,4-dihydrobenzo[f]quinoxalin-6(2H)-one, which exhibits the keto-amine arrangement. Density functional theory (DFT) calculations confirmed the preference of 5-chlorobenzo[f]quinoxalin-6-ol and of the derivatives containing H and CH3 groups in place of the Cl atom for the enol-imine tautomer. It is suggested that the enol-imine structure is preferred for 5-chlorobenzo[f]quinoxalin-6-ol as a consequence of the higher aromatic character of this structure in comparison with the keto-amine form. DFT calculations carried out on the two tautomers of the benzo[a]phenazin-5(7H)-ones analogous to the benzo[f]quinoxalin-6(4H)-ones showed that the relative stabilities are dominated by solvation effects in the first case and the degree of aromaticity, in the latter.

ChemInform Abstract: 1,3-Cycloaddition of Nitrile Oxides to Cyclic and Open-Chain 4-Oxo-2-sulfinylbut-2-enoic Acid Derivatives.

Abstract The reactions of tert-butyl (E)-4,4-diethoxy-2-p-tolylsulfinylbut-2-enoate with benzonitrile, acetonitrile, and bromoformonitrile oxides yield isoxazoles. However, (S5,SS)- and (R5,SS)-5-ethoxy-3-p-tolylsulfinylfuranones with benzonitrile oxide afford isoxazolines. The reactivity of the double bond as a dipolarophile is strongly increased by the sulfinyl group. This is also the case of the regioselectivity, which usually is opposite to that exhibited by dipolarophiles lacking the sulfinyl group. Electrostatic interactions seemingly explain this behaviour. The π-facial selectivity of the reactions with the cyclic dipolarophiles is dependent on steric effects, but some role seems to be exerted by electrostatic attraction.

First Example of s-BuLi/(-)-Sparteine-Mediated Chiral Deprotonation of a Piperazine and Proof of the Sense of Induction

This paper describes the first known example of a (-)-sparteine-mediated asymmetric deprotonation of a piperazine. Reaction of TERT-butyl 4- TERT-butylpiperazine-1-carboxylate with S-BuLi in the presence of (-)-sparteine at -78 °C and quenching with carbon dioxide proceeded in good yield and with a high degree of selectivity (er = 89:11). X-ray crystal structure analysis on a chiral derivative confirmed the R-enantiomer was the major product. This methodology was employed as a route to an advanced chiral intermediate that was used in parallel synthesis of a range of molecules of medicinal interest. Optimisation of the chemistry used to introduce a TERT-butyl group onto a piperazine nitrogen is also described.

Reactions of In Situ Generated N-Boc Nitrones with Aromatic and Heteroaromatic Grignard Reagents: Application to the Synthesis of Zileuton

A new class of alpha-aromatic-N-hydroxylamines has been prepared by reaction of tert-butyl (phenylsulfonyl)alkyl-N-hydroxycarbamates with aromatic and heteroaromatic Grignard reagents. Reactions proceed via a base-assisted elimination of the phenylsulfonyl group leading to N-Boc nitrones. This methodology has been applied to the synthesis of zileuton.

One‐Pot Synthesis of Furo[3,2‐c]oxepin‐4‐one Derivatives by the CAN‐Mediated Reaction of tert‐Butyl 2‐(2‐Hydroxytetrahydrofuran‐2‐yl)acetates with Alkenes.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Efficient Synthesis of Novel Polyfunctionalised 4,5′-Bithiazol-4′-ol Derivatives

2-Thiazolin-4-one derivatives, obtained by reaction of tert-butyl (3-methoxy-1-methyl-3-oxoprop-1-enyl)diazenecarboxylate with aryl thioamides, were transformed into 5-bromoacetyl-4-hydroxythiazole derivatives by polymer-supported reagents and simple work-up procedures. The compounds thus synthesised were coupled with thioamides bearing valuable functional groups affording novel polyfunctionalised 4,5'-bithiazol-4'-ol derivatives.

Stereoselective synthesis of the alpha-glycoside of a KDO "C"-disaccharide.

The reaction of tert-butyl (4,5,7, 8-tetra-O-acetyl-3-deoxy-alpha-D-manno-2-octulopyranosyl chloride)onate donor 7 with the 6-formylgalactopyranoside acceptor 4 in the presence of SmI(2) provided only the KDO alpha-C-disaccharide 8. The bulky tert-butyl ester in the donor was used to reverse the stereochemical outcome of C-glycosylation, stereoselectively forming the alpha-"C"-disaccharide of KDO.

1,3-cycloaddition of nitrile oxides to cyclic and open-chain 4-oxo-2-sulfinylbut-2-enoic acid derivatives

The reactions of tert-butyl ( E)-4,4-diethoxy-2- p-tolylsulfinylbut-2-enoate with benzonitrile, acetonitrile, and bromoformonitrile oxides yield isoxazoles. However, ( S 5, S S)- and ( R 5, S S)-5-ethoxy-3- p-tolylsulfinylfuranones with benzonitrile oxide afford isoxazolines. The reactivity of the double bond as a dipolarophile is strongly increased by the sulfinyl group. This is also the case of the regioselectivity, which usually is opposite to that exhibited by dipolarophiles lacking the sulfinyl group. Electrostatic interactions seemingly explain this behaviour. The π-facial selectivity of the reactions with the cyclic dipolarophiles is dependent on steric effects, but some role seems to be exerted by electrostatic attraction.

Dynamic kinetic resolution utilizing 2-oxoimidazolidine-4-carboxylate as a chiral auxiliary: Stereoselective synthesis of α-amino acids by Gabriel reaction

A Highly stereoselective Gabriel reaction via dynamic kinetic resolution utilizing 2-oxoimidazolidine-4-carboxylate as a chiral auxiliary was exploited. The reaction of tert-butyl (4 S)-1-methyl-3-(2-bromopropionyl)-2-oxoimidazolidine-4-carboxylate ( 2a) with potassium phthalimide at room temperature predominantly afforded tert- butyl (4S)-1- methyl-3-((2S)-2-( phthaloylamino)propionyl)-2-oxoimidazolidine-4-carboxylate ((S,S)- 5a) in a good yield which was derived to l- alanine derivative ( 7) by removal of the chiral auxiliary.

Dynamic kinetic resolution utilizing a chiral auxiliary by stereoselective SN2 alkylation with malonic ester enolate

Dynamic kinetic resolution by highly stereoselective carbon-carbon bond formation utilizing 2-oxoimidazolidine-4-carboxylate as a chiral auxiliary was exploited. The reaction of tert-butyl(4 S)-1-methyl-3-(2-bromopropionyl)-2-oxoimidazolidine-4-carboxylate ( 1) with sodium dimethyl malonate in HMPA at room temperature predominantly afforded tert-butyl(4 S)-1-methyl-3-((2 R)-2-methyl-3,3-bis(methoxycarbonyl)propionyl)-2-oxoimidazolidine-4-carboxylate ( (S,R)- 2a ) in a good yield.

Dynamic kinetic resolution by stereospecific amination utilizing 2-oxoimidazolidine-4-carboxylate as a novel chiral auxiliary

A novel type of dynamic kinetic resolution by stereospecific amination was exploited utilizing 2-oxoimidazolidine-4-carboxylate 1 as a chiral auxiliary. The reaction of tert-butyl (4 S)-1-methyl-3-(2-bromopropionyl)-2-oxoimidazolidine-4-carboxylate ( 2) with benzylamine in HMPA in the presence of K 2CO 3 or Et 3N at 25°C predominantly afforded tert-butyl (4 S)-1-methyl-3-((2 R)-2-benzylaminopropionyl)-2-oxoimidazolidine-4-carboxylate (( S,R)- 4) in nearly quantitative yield.

An europium(III) complex as an efficient catalyst for the Michael reaction of α,β-enones with ketene silyl acetals: LIS-NMR analysis for the transition state through complexation between europium(III) catalyst and enones

The europium(III) complex, Eu(dppm) 3, is found to be an efficient catalyst for the Michael reactions of α, β- enones with ketene silyl acetals. The high level of erythro selectivity obtained in the reaction of tert-butyl ( E)- propenyl ketones ( 2c) with (E)-1-tert-butoxy-1-[(trimethylsilyl)oxy]propene ( 3d) is rationalized on the basis of the LIS-NMR analysis of the europium(III) catalyst/enone 2c complex.

2-oxoimidazolidine-4-carboxylate as a novel chiral auxiliary for kinetic resolution

A kinetic resolution by stereospecific amination using 2-oxoimidazolidine-4-carboxylate as a novel chiral auxiliary was investigated. The reaction of tert-butyl (4 S)-1-methyl-3-(2-bromopropionyl)-2-oxoimidazolidine-4-carboxylate ( 5) with an equimolar benzylamine in CH 2Cl 2 proceeded stereospecifically to afford tert-butyl (4 S)-1-methyl-3-(2 R)-2-benzylaminopropionyl)-2-oxoimidazolidine-4-carboxylate (( S,R)- 4) in a good yield, while ( S,R)- 5 was recovered quantitatively.

Über die Reaktion von tert ‐Butyl( tert ‐butylimino)phosphan mit tert ‐Butyl‐( tert ‐butylimino)boran

On the Reaction of tert-Butyl(tert-butylimino)phosphane with tert-Butyl(tert-butylimino)borane Contrary to the [2 + 2] cycloaddition reaction of aminoiminophosphanes with iminoboranes, the title compounds react to yield the heterocyclic products 7 and 9, the structures of which were determined by means of spectroscopic methods and, in the case of 9, additionally by X-ray structural analysis. Further investigations on the reaction mechanism suggest that the first step of the reaction sequence is an oxidative [2 + 1] cycloaddition of the iminophosphane 3 to 2.

Sterically Hindered Silylamines. The Preparation of Sometert-Butyldiphenylsilylamines

Abstract Reactions of tert-butyl (chloro) diphenylsilane with ammonia, primary and secondary amines, or their lithium salts produce compounds having the general formula t-Bu(C6H5)2SiNRR'. These compounds are viscous, high-boiling liquids with high thermal stabilities and unusually low reactivities toward hydrolysis. Comparisons are made to the tert-butyldimethylsilyl analogues.

ChemInform Abstract: Sterically Hindered Silylamines. Preparation of Some Secondary and Tertiary tert‐ Butyldimethylsilylamines.

AbstractDie Silylierung der aus den Aminen (II) in situ hergestellten Lithium‐ Salze liefert höhere Ausbeuten an den hydrolysestabilen, im Titel genannten Verbindungen (III) als die direkte Umsetzung der Amine (II) mit dem Silylchlorid (I).