Alkylation base mediated

In this method, Furstner converts N-BOC protected pyrrole to the 2,5-dibromo compound (122) with NBS and this is followed by metalation and carbomethoxylation with t-butyl lithium in THF and subsequent trapping of the metalated species with methyl chloroformate to yield a pyrrole diester (123). Bromination of this diester at positions 3 and 4 with bromine in water followed by Suzuki cross-coupling with 3,4,5-trimethoxyphenyl boronic acid yields the symmetrical tetrasubstituted pyrrole (125). Base-mediated N-alkylation of this pyrrole with 4-methoxyphenethyl bromide produces the key Boger diester (126) and thereby constitutes a relay synthesis of permethyl storniamide A (120). 

A possible mechanism for the P-alkylation of secondary alcohols with primary alcohols catalyzed by a 1/base system is illustrated in Scheme 5.28. The first step of the reaction involves oxidation of the primary and secondary alcohols to aldehydes and ketones, accompanied by the transitory generation of a hydrido iridium species. A base-mediated cross-aldol condensation then occurs to give an a,P-unsaturated ketone. Finally, successive transfer hydrogenation of the C=C and C=0 double bonds of the a,P-unsaturated ketone by the hydrido iridium species occurs to give the product. 

The base-mediated intramolecular alkylation of glucose derivatives provides highly functionalized cyclopentanes in good yield and without any of the expected side reactions (Equation 60) <2000TL5507, 2001T4729>. 

Not surprisingly, ILs have been analyzed using alkyl-based reversed phase [20] as well as cation-exchange chromatography [21,22]. However, the rich potential interaction chemistries of ILs may also be inferred from the retention behavior of imidazolium- and pyridinium-based ILs on phenyl-based stationary phases which can supply aromatic ji-ji interaction capability [23]. The multiple modes of interaction between the imidazolium and the phenyl phase are illustrated in Figure 5.1. In this study, it was reported that the role of aromatic ji-ji interactions in the separations of IL cations could be mediated by the addition of acetonitrile. 

Substituted 1,2,3-triazole 1-oxide 448 can be prepared by N-oxidation of 1-substituted 1,2,3-triazoles 457, by N-alkylation of 1-hydroxy-1,2,3-triazoles 443, by cyclization of triazene 1-oxides 460, or by rearrangement of 2-substituted 1,2,3-triazole 1-oxides 445 (R=PMB). Finally, base-mediated ring opening of pyrimidinediones 463 offers a route to 464. 

Nitriles are well known to undergo acid and alkaline hydrolysis (Figure 13.5), but there is only one recent report of neutral hydrolysis. Thus, methacrylonitrile, even though it is conjugated with an alkenyl substituent, should undergo both acid-catalyzed and base-mediated hydrolysis via a pathway similar to that for alkyl and aryl nitriles. The amide is a likely intermediate product for nitrile hydrolysis, but it is reactive as well and can undergo acid- and base-mediated hydrolysis to the carboxylic acid and ammonia. The... 

Radical decarboxylative alkylation of heteroaromatic bases mediated by [bis(acyloxy)iodo]arenes... 

The simplest 1,3-dipolar cycloadditions of diazomethane were presented in Figure 12.33. Diazomethane is generated from sulfonamides or alkyl carbamates of A-nitrosomethylamine. The preparation shown in Figure 12.37 is based on the commercially available para-toluenesulfonylmethylnitrosamide (Diazald). In a basic medium, this amide forms a sulfonylated diazotate A by way of a [1,3]-shift, which then undergoes a base-mediated 1,3-elimination (cf. Section 4.1.1). 

The asymmetric synthesis of 4-alkyl-4-carboxy-2-azetidinones 18 has been achieved through base-mediated intramolecular cyclization of the corresponding Af-a-chloroacetyl derivatives bearing (+)- or (-)-10-(W,A,-dicyclohexylsulfamoyl)isobomeol as chiral auxiliary (ee up to 82%) <02JOC3953> <02H501>. 

A mechanistic rationale commences with the oxidative addition of iodo benzene to a Pd(0) complex furnishing a phenyl-Pd species that readily inserts norbornene to furnish an alkyl Pd-intermediate 28 that undergoes base-mediated CH activation of the ortho position of the phenyl ring (Scheme 10). 

N-Acyl derivatives (lb. Id, le, If, Ig, Ih, Ij, Im and lo) were prepared from either the protected adenosine 3, or its chloro analogue, by standard procedures (Scheme 2). N-alkyl derivatives (li, Ik, 11 and In) were prepared by the base mediated alkylation of compound 4 followed by acid catalysed deprotection, e.g. compound li was prepared from compound 4 in a 22% overall yield. Dealanylascamycin la was prepared by the hydrolysis of the chloro analogue of compound 4. ... 

Clark, A.J., Al-Faiyz, Y.S.S., Patel, D. and Broadhurst, M.J. (2001) Rearrangement of unactivated A-alkyl-O-benzoyl hydroxamic acid derivatives with phosphazene bases. Tetrahedron Letters, 42, 2007-2009 Clark, A.J., Patel, D. and Broadhurst, M.J. (2003) Base-mediated reaction of A-alkyl-O-acyl hydroxamic acids synthesis of 3-oxo-2,3-dihydro-4-isoxazole carboxylic ester derivatives. Tetrahedron Letters, 44, 7763-7765. 

Pyrazinoquinodimethanes were found to undergo 4+2 cycloaddition to [60]fullerene under thermal- or microwave irradiation-assisted conditions <97JOC3705>. The base-mediated alkylation of quinoxalin-2(l/f)-one with co-phenylalkyl halides affords a mixture of N- and O-functionalized products that are separable by chromatography <97H357>. 

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