Nucleophile 2-amino alcohol

Nucleophilic ring opening of epoxides by ammonia (Section 16.12) The strained ring of an epoxide is opened on nucleophilic attack by ammonia and amines to give p-amino alcohols. Azide ion also reacts with epoxides the products are p-azido alcohols. 

Notwithstanding the expected and also observed high reactivity of the intermediate immonium ions, the stabilization of the exocyclic double bond in the pyrrolidino derivative evidently prevents rapid nucleophilic attack of water and the hydration of this ion to the amino alcohol becomes a slow general base-catalyzed process in weakly acidic solutions [Eq. (6)]. 

Dehydrogenation of amino alcohols of type 40 affords even bicyclic compounds 41, the formation of which can be explained by nucleophilic attack of the hydroxyl group on the formed enamine salt (133,134). 

Quite a number of asymmetric thiol conjugate addition reactions are known [84], but previous examples of enantioselective thiol conjugate additions were based on the activation of thiol nucleophiles by use of chiral base catalysts such as amino alcohols [85], the lithium thiolate complex of amino bisether [86], and a lanthanide tris(binaphthoxide) [87]. No examples have been reported for the enantioselective thiol conjugate additions through the activation of acceptors by the aid of chiral Lewis acid catalysts. We therefore focussed on the potential of J ,J -DBFOX/ Ph aqua complex catalysts as highly tolerant chiral Lewis acid catalyst in thiol conjugate addition reactions. 

Substitution of an additional nitrogen atom onto the three-carbon side chain also serves to suppress tranquilizing activity at the expense of antispasmodic activity. Reaction of phenothia zine with epichlorohydrin by means of sodium hydride gives the epoxide 121. It should be noted that, even if initial attack in this reaction is on the epoxide, the alkoxide ion that would result from this nucleophilic addition can readily displace the adjacent chlorine to give the observed product. Opening of the oxirane with dimethylamine proceeds at the terminal position to afford the amino alcohol, 122. The amino alcohol is then converted to the halide (123). A displacement reaction with dimethylamine gives aminopromazine (124). ... 

Bartoli recently discovered that by switching from azide to p-anisidine as nucleophile, the ARO of racemic trans- 3-substituted styrene oxides could be catalyzed by the (salen)Cr-Cl complex 2 with complete regioselectivity and moderate selectivity factors (Scheme 7.36) [14]. The ability to access anti-P-amino alcohols nicely complements the existing methods for the preparation of syn-aryl isoserines and related compounds [67] by asymmetric oxidation of trans-cinnamate derivatives [68]. 

The regioselective ring-opening of vinyloxiranes by nitrogen nucleophiles offers an attractive route to vie-amino alcohols, compounds of much recent interest. As with oxygen nucleophiles, the stereochemistry of the reaction can be controlled by choice of reaction conditions aminolysis of 25, for example, affords anti-amino alcohol 26 in excellent yield and diastereoselectivity (Scheme 9.21) [48, 96, 97], and... 

Additions of oxygen and nitrogen nucleophiles to vinyloxiranes can be achieved with Pd(0) catalysis [103, 104]. Acetate, silanols, amines, sulfonamides, and azide have been used as nucleophiles, and the stereochemical outcome of these additions, where applicable, is normally the result of two consecutive SN2 reactions. This is demonstrated by the additions of NaNHTs to vinylepoxides 29 and 30, affording syn- and anti-amino alcohols 31 and 32, respectively, in good yields and with high diastereoselectivities (Scheme 9.22) [105]. 

Treatment of m-butyl (S )-4-formyl-2,2-dimethyl-3-oxazolidinccarboxylate ( Garner aldehyde, 3), readily available from /V-Boc-l-serine and configurationally extremely stable49,50, with various nucleophiles preferentially yields the n n(nonchelation)-diastereomeric amino alcohols 4 in high chemical yield51 -55,57-61. 

Oxetanes are significantly less reactive with nucleophiles due to diminished ring strain. Under certain conditions, however, amines can open oxetanes to give amino alcohols. tert-Butylamine reacts with oxetanes in the presence of Yb(OTf)3 to give 3-hydroxy amines. Lithium tetrafluorohorate has also been used for this... 

Amides can add to aldehydes in the presence of bases (so the nucleophile is actually RCONH ) or acids to give acylated amino alcohols, which often react further to give alkylidene or arylidene bisamides. If the R group contains an a hydrogen, water may split out. 

This work has been extended to transesterification with secondary alcohols [23], and of phosphonate esters [24], Movassaghi and co-workers have demonstrated that NHCs effectively catalyse the amidation of esters with amino alcohols, although an alternative mechanism involving the NHC acting as a Brpnsted base, resulting in nucleophilic activation of the alcohol for an initial transesterification event, followed by rapid O- to iV-acyl transfer, has been proposed [25, 26],... 

The proline-catalyzed reaction has been extend to the reaction of propanal, butanal, and pentanal with a number of aromatic aldehydes and proceeds with high syn selectivity.197 The reaction can also be carried out under conditions in which the imine is formed in situ. Under these conditions, the conjugative stabilization of the aryl imines leads to the preference for the aryl imine to act as the electrophile. A good yield of the expected P-aminoalcohol was obtained with propanal serving as both the nucleophilic and the electrophilic component. The product was isolated as a 7-amino alcohol after reduction with NaBH4. 

Taking Tomioka s pioneering work [8] as a precedent, we have screened 13-amino alcohols as chiral modifiers [9] in the nucleophilic addition of lithium 2-pyridinylacetylide 6 to the pMB protected ketimine 5. We were pleased to discover that when 5 was treated with a mixture prepared from 1.07 equiv each of quinine and 2-ethynylpyridine by addition of 2.13 equiv of n-BuLi in THF at -40 to -20 °C, the desired adduct 19 was obtained in 84% yield with maximum 64% ee. Soon after, we found selection of the nitrogen protective group had great influence on the outcome of the asymmetric addition and the ANM (9-anthranylmethyl)... 

A typical second step after the insertion of CO into aryl or alkenyl-Pd(II) compounds is the addition to alkenes [148]. However, allenes can also be used (as shown in the following examples) where a it-allyl-r 3-Pd-complex is formed as an intermediate which undergoes a nucleophilic substitution. Thus, Alper and coworkers [148], as well as Grigg and coworkers [149], described a Pd-catalyzed transformation of o-iodophenols and o-iodoanilines with allenes in the presence of CO. Reaction of 6/1-310 or 6/1-311 with 6/1-312 in the presence of Pd° under a CO atmosphere (1 atm) led to the chromanones 6/1-314 and quinolones 6/1-315, respectively, via the Jt-allyl-r 3-Pd-complex 6/1-313 (Scheme 6/1.82). The enones obtained can be transformed by a Michael addition with amines, followed by reduction to give y-amino alcohols. Quinolones and chromanones are of interest due to their pronounced biological activity as antibacterials [150], antifungals [151] and neurotrophic factors [152]. 

An amino alcohol can be formed in situ by the reaction of an iV-formylpiperizine 79 with epoxide 78 which then can be induced to cyclize to give the spiroaziridinium salt 80 (Equation 17) <2004TL4175>. The spiroaziridinium was not isolated but instead trapped by reaction with an amine nucleophile (cf. Section 12.20.6.1). 

One of the most well used methods for the synthesis of aziridines involves a two (or sometimes more) step process in which an epoxide is opened by a nitrogen nucleophile. The resulting P-amino alcohol (e.g. 79) is then converted to an aziridine via a number of different processes. This method is generally not broadly applicable when a variety of different groups on the nitrogen of the aziridine are desired. A useful method to convert an epoxide to a number of different /V-sulfonyl aziridines (e.g. 80) has been reported <06S425>. Simple addition of a sulfonamide to an epoxide provides high yields of 79 which is readily closed to form the aziridine. 

Nucleophilic addition of metal alkyls to carbonyl compounds in the presence of a chiral catalyst has been one of the most extensively explored reactions in asymmetric synthesis. Various chiral amino alcohols as well as diamines with C2 symmetry have been developed as excellent chiral ligands in the enantiose-lective catalytic alkylation of aldehydes with organozincs. Although dialkylzinc compounds are inert to ordinary carbonyl substrates, certain additives can be used to enhance their reactivity. Particularly noteworthy is the finding by Oguni and Omi103 that a small amount of (S)-leucinol catalyzes the reaction of diethylzinc to form (R)-l-phenyl-1 -propanol in 49% ee. This is a case where the... 

The nucleophilic addition of nitroalkane to carbonyl groups is known as the Henry reaction. The products of the Henry reaction are 2-nitroalkanols,115 which are useful intermediates for nitroalkenes, 2-amino alcohols, and 2-nitro-ketones. However, this does not always give high yields because of the possible O-alkylation in preference to C-alkylation during the Henry reaction. 

Fluorine-containing compounds can also be synthesized via enantioselective Reformatsky reaction using bromo-difluoroacetate as the nucleophile and chiral amino alcohol as the chiral-inducing agent.86 As shown in Scheme 8-41, 1 equivalent of benzaldehyde is treated with 3 equivalents of 111 in the presence of 2 equivalents of 113, providing a,a-difluoro-/ -hydroxy ester 112 at 61% yield with 84% ee. Poor results are observed for aliphatic aldehyde substrates. For example, product 116 is obtained in only 46% ee. 

Dimethylaminoethane-2-ol (20) is a compound that, by virtue of its nucleophilic center (Me2NH+C2H40), is employed to convert protected segments bound to supports as benzyl esters into acids by transesterification into dimethylaminoethyl esters [C(=0)0C2H4NMe2] that are hydrolyzable by a dimethylformamide-water (1 1) mixture. Compound 20 readily forms esters from acid chlorides. The hydrolysis and esterification are facilitated by anchimeric assistance by the adjacent nitrogen atom (see Section 2.10). The amino alcohol also reacts with dichloromethane. 

A variety of ie.so-epoxidcs could be selectively ring-opened this way with e.e. s as high as 97% [28], The azides can be converted to 1,2-amino alcohols, which are very desirable synthetic intermediates. Surprisingly, the mechanism of the ARO (asymmetric ring-opening) was more complicated than expected [29], First, it turned out that the chloride ion in Cr-salen was replaced by azide. Secondly, water was needed and HN3 rather than Me3SiN3 was the reactant nucleophile. Thirdly, the reaction rate was found to be second order in catalyst concentration, minus one in epoxide (cyclopentene oxide), and zero order in HN3 [30],... 

At first sight, it appears that it should be feasible to prepare such esters regioselectively using a similar biocatalytic approach to that employed for the 6- and 7-amino acylation of 6-APA and 7-ADCA shown above. Unfortunately, owing to the poor nucleophilicity of alcohols, biocatalytic esterification in aqueous media is far more challenging than amida-tion. Therefore, it was not until the pioneering work of Klibanov and co-workers, who first demonstrated the use of enzymes in neat organic solvents, that this option became viable (see Section 1.4). 

The amino alcohol intermediate is analogous to the hemiacetal, and both undergo protonation and loss of water, facilitated by the heteroatom. The iminium cation can then lose a proton, but the oxonium cation has no proton to lose instead, it is attacked by a nucleophile, namely a second molecule of alcohol. 

Cdrdova has shown that using unprotected iV-hydroxycarbamates 71 as the nucleophile with diarylprohnol ether 30 as catalyst gave direct access to 5-hydrox-yisoxazolidines 72 (91-99% ee) which are convenient precursors to p-amino alcohols and p-amino acids (Scheme 31) [110], Interestingly, these reactions proceed efficiently (3-16 h) without the need for an additional co-acid unlike the majority of other iminium ion catalysed transformations, an unexpected result which highlights the need for further mechanistic understanding. 

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