Reaction with Miscellaneous Electrophiles

The halogenation of enamines is formally analogous to protonation with salt formation. Thus the steroidal enamine (164) undergoes bromination (7/5) to give the j8-bromo iminium bromide (165), which is readily hydrolyzed to the /5-bromo aldehyde (166). 

This method of bromination has been employed in the selective bromination (777) of the ketone (167). While direct bromination results in bromination not only in the position alpha to the ketone but also in the aromatic ring, bromination of the enamine (168) and subsequent hydrolysis gave only the monobrominated product (169). 

Chlorination of enamincs has also been reported (42,118). Thus the trichlorovinylamine (170) has been chlorinated to 171, which was not isolated but treated with hydrogen sulfide to give the thioamide (172) (118). 

A stable chloroiminium chloride (173) has been isolated from the chlorination of the heterocyclic enamine (174) (42). 

Stable )3-chloro and bromo enamines have recently been obtained by reaction of enamines with the corresponding N-halosuccinimides (118a). 

---

The reactions of the homocyclic ring are considered in three parts attack by electrophiles attack by nucleophiles and transformations involving substituent groups, together with miscellaneous reactions. Unless otherwise stated common behaviour is assumed for benzofurazans and benzofuroxans. 

Electrophilic Opening 20 Nucleophilic Opening 22 Cyclisation Reactions 26 Reduction and Elimination Reactions 28 Photochemical Reactions 30 Reactions with Organometallic Compounds 30 Miscellaneous Reactions 34... 

As is the case with miscellaneous nucleophilic cyclizations (Chapter 21), several electrophilic cyclizations leading to the indole ring do not appropriately fit into any of the preceding chapters in this category. As with the aforementioned chapter, 1 will mention the anthor of each new electrophilic indoliza-tion becanse fnture work might elevate that reaction to Name statns. As with all ionic reactions, there is an electrophilic and nncleophilic component. Therefore, the inclusion of electrophilic indole ring syntheses in this ch ter can be viewed as somewhat arbitrary, as was the case in Chapter 21 (Miscellaneons Nncleophilic Cyclizations). 

Arasabenzene, with chromium, 5, 339 Arcyriacyanin A, via Heck couplings, 11, 320 Arduengo-type carbenes with titanium(IV), 4, 366 with vanadium, 5, 10 (Arene(chromium carbonyls analytical applications, 5, 261 benzyl cation stabilization, 5, 245 biomedical applications, 5, 260 chiral, as asymmetric catalysis ligands, 5, 241 chromatographic separation, 5, 239 cine and tele nucleophilic substitutions, 5, 236 kinetic and mechanistic studies, 5, 257 liquid crystalline behaviour, 5, 262 lithiations and electrophile reactions, 5, 236 as main polymer chain unit, 5, 251 mass spectroscopic studies, 5, 256 miscellaneous compounds, 5, 258 NMR studies, 5, 255 palladium coupling, 5, 239 polymer-bound complexes, 5, 250 spectroscopic studies, 5, 256 X-ray data analysis, 5, 257... 

This section brings together a miscellaneous set of reactions all of which require a parent nucleus that is aromatic, rc-excessive, and electronically equipped to support an electrophilic attack adjacent to the amino group. Understandably, rather severe conditions are often required. Common substituents found in the product are alkyl, aryl, amino, and oxo groups. For example, 2-aminonaphthalene hydrochloride, when refluxed for 2 days with an excess of sodium dicyanimide [NaN(CN)2] in octanol, gave 1,3-diamino-benzo[/]quinazoline (54) in good yield the method was also suitable for... 

Miscellaneous. Double lithiations of the parent compounds give the dianions (25) and (26), both of which react with electrophiles preferentially at the benzyl positions. Addition of RLi to the carbonyl group of compound (27), followed by reduction of the initial product, gives access to 4-alkyl-2,6-di-t-butylanilines. Low-temperature reactions between aldehydes and RLi in the presence of asymmetric auxiliaries such as (28) give secondary alcohols with up to 40% enantiomeric... 

Miscellaneous reactions of cr-sulphonyl carbanions with electrophiles include processes involving arylsulphonylmethyl methyl ether anions, cr-sulphinyl sulphone anions, perfluorobutylsulphonylmethylmagnesium halides, nucleophilic substitution in aromatic nitro-compounds by cr-halogenosulphonyl... 

Miscellaneous Reactions.—a-Alkoxylated a-lithioacetates may be alkylated,may react with ketones (the products from which cyclize to f3-lactones, themselves precursors of enol ethers by CO2 elimination" ), and may be condensed with lactones, as applied in a synthesis of natural product derivatives.The trianion derived from PhCH(0H)C02H is. C-alkylated but only in mediocre yield.The anions PhSCHCO and PhSCHC02Me react efficiently with electrophiles however, the former adds 1,2 to a, 8-unsaturated ketones, whereas the latter adds 1,4- ... 

Miscellaneous Reactions. Isobutene, as the carbenium ion source for Ritter reactions, produces Al-r-butyl amides (eq 34). Isobutene undergoes highly regioselective cycloaddition with isocyanate to form azetidinones and with nitrones to yield isox-azolidines (eqs 35 and 36). Allyl thioethers are formed by the electrophilic addition of Benzenesulfenyl Chloride to isobutene (eq 37). Alkenylphosphonous dichlorides and alkenylthionophosphonic dichlorides are also formed by addition of PCI5 and P2S5 (eqs 38 and 39). ... 

---