Alkenyl anilines

The 2-alkenyl sulfinamides appeared to be slightly unstable. They could, however, be quickly converted into anilines by base-catalyzed hydrolysis in good yields (Scheme 52) <91JOC5059 91T8855>. This general route to 2-alkenyl anilines is regioselective, but not stereoselective. 

In 1998, Harmata and co-workers <98T9995> published a new synthesis of 2-alkenyl anilines. The silylated 2,1-benzothiazines 187 could be deprotonated by n-BuLi and alkylated by different electrophiles. The corresponding products could be desilylated by fluoride with concomitant cleavage of the carbon-sulfur bond to give 2-alkenylsulfinanilides that can then be hydrolyzed by base to the anilines 195 in good yields (Scheme 55). 

Stoichiometric Pd(II)-mediated oxidative cyclization of alkenyl anilines to indoles. Cf. Wacker oxidation. 

Surprisingly high ee values have been independently recorded by Bailey and Mealy and Sanz Gil and Groth for the cyclocarboUthiation of 2-lithio-Af-(2-alkenyl)anilines in the presence of (—)-sparteine (11) to form 1,3-disubstituted indolines... 

The reaction is often used to effect ring closure.The Friedldnder quinoline synthesis is an example where ortho alkenyl aniline derivatives give the quinoline, 20. The alkene derivative can be prepared in situ from an aldehyde and a suitably functionalized ylid. ... 

Heck cyclization reactions of o-halo-A-(2-alkenyl)anilines have proven useful for the development of type Ic approaches to indoles. Recent applications include the preparation of a... 

In the mid-1990s, a related sequence of reactions has been used for the regioselective preparation of 2-allyl and 2-alkenyl anilines from 2,1-benzothiazines <958713,95TL4769>. 

Electrochemically generated nickel is very selective for the reduction of ai compounds into anilines, in which alkenyl, alkyhyl, halo, cytino, formyl, ind benzyloxy groups are not affected. Sodium snlfide has been used for the selective reduction of at group in the presence of aliphatic nitro groups (Tq. 6.44. ... 

Pr)4, " borohydride-exchange resin,and formic acid. When the last is used, the process is called the Wallach reaction. Conjugated aldehydes are converted to alkenyl-amines with the amine/silica gel followed by reduction with zinc borohydride.In the particular case where primary or secondary amines are reductively methylated with formaldehyde and formic acid, the method is called the Esch-weiler-Clarke procedure. It is possible to use ammonium (or amine) salts of formic acid, " or formamides, as a substitute for the Wallach conditions. This method is called the Leuckart reaction,and in this case the products obtained are often the N-formyl derivatives of the amines instead of the free amines. Primary and secondary amines can be iV-ethylated (e.g., ArNHR ArNREt) by treatment with NaBH4 in acetic acid. Aldehydes react with aniline in the presence of Mont-morillonite KIO clay and microwaves to give the amine. Formaldehyde with formic acid converts secondary amines to the N-methyl derivative with microwave irradiation. 

The pyridine ligand in some alkenyl cobalt(III) DMG complexes may be replaced by methyl or ethyl phosphite by addition of the phosphite to a solution of the (DMG)2 complex in ethanol. In a similar manner aniline may be displaced by (CH30)3P from [CH2=CHCo(DMG)2C6HjNH2] (129). 

Palladium-catalyzed room-temperature >rtfe>-alkenylations of anilides have been recently reported, employing benzoquinone as a stoichiometric oxidant. A kinetic isotope effect kn/koof 3 points to a slow C-H functionalization step. Electron-rich acetanilides react faster whereas anilines are unreactive (Equation (138)).120... 

Very interesting results were obtained from the reaction of magnesium alkylidene carbenoids with mefa-substituted arylamines (Table 8) . The reaction of magnesium alkylidene carbenoids 157 and 161 with three mefa-substituted anilines was carried out and the results are summarized in Table 8. The reaction of 157 with meta-anisidine gave two products 163 and 164 (in a 30 13 ratio) in 43% yield. The main product was found to have the alkenyl group at the more hindered position (163). As shown in the Table, all the other meto-substituted aniline derivatives also gave the more hindered alkenylated compounds as the main product in variable ratio. 

The use of alkenyl boronic acid derivatives 50, which are readily prepared via hydroboration or bromoboration of alkynes, affords the corresponding p,y-unsaturated amino acids (e.g. 52-57) in a geometrically pure form [34], A variety of amines 48, including primary and secondary amines, anilines, amino alcohols and hydroxylamines can effectively participate in this process, while the alkenyl boronic acid can contain alkyl, aryl or bromo-substituents. Although the alkenyl amino acid side chain is introduced through the boronic acid component, the use of more substituted a-keto acids 49 allows the simultaneous incorporation of an additional a-substituent (e.g. 57). 

Anatoxin-a, via enyne metathesis, 11, 297 Ancillary ligands, in alkene polymerization, 11, 697 Anilides, or/itf-alkenylations, 10, 144 Anilido complexes, with mono-Cp Ti(IV), 4, 415 Anilines... 

Auch die nach verschiedenen Methoden gut zuganglichen Phosphorsaure-alkyl( 1-alkenyl- bzw. aryl)ester-bis-[trimethylsilylester] lassen sich bereits mit Wasser bei 0-20°zu den Monoestem hydrolysieren33. Durch Zugabe von Ethanol/Anilin in Tetrahydrofuran werden bei 25° die Anilinium-Salze34, mit Natriumethanolat in Diethylether die Natrium-Salze in hohen Ausbeuten erhalten35 z.B. ... 

Tetrahydrocarbazoles and related fused systems have been accessed by a route relying on palladium-catalyzed tandem formation of alkenyl and aryl C-N bonds. For instance, the starting triflate 477 could be efficiently transformed into the target system 478 by amination with aniline (Equation 133) <2005AGE403>. Annulation of (2-triflyloxy)phenethyl carbonates with amides in the presence of a palladium catalyst has been used as a route to various N-substituted indoline derivatives <2005OL4777>. 

TABLE 2. Nucleophilic substitution reactions of anilines at arylalkyl-, alkenyl- and alkynylmethyl carbons... 

Synthesis of enantiomerically enriched secondary amines (168) with excellent ee values, through the tandem, intermolecular hydroamination with primary amines (166) /transfer hydrogenation of alkynes (167), using a the gold(I) complex-chiral phosphoric acid (127) protocol, has been developed by Che and Liu (Scheme 44). A wide variety of aryl, alkenyl, and aliphatic alkynes as well as anilines with different electronic properties were tolerated. 

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