Pyridines 4-ferf-amino

The term ferf-amino effect is used to describe ring-closure of N, A -dialkyl-substituted anilines with an unsaturated electrophilic ortho substituent to afford fused tetrahydroquinolines [22] or other iV-heterocycles [15, 19, 20,46, 85-87]. The terf-amino effect has been widely utilized in the synthesis of pyridine, pyrimidine, and pyridazine derivatives, which has been well reviewed by Matyus et al. [15]. 

In 1959 Shchukina et a I. 56 showed that the addition of pyridine to DCC increases the yield (65-85%) of depsipeptides constructed from Z-protected amino acids and serine, threonine, or salicylic acid derivatives. The ferf-butyl ester of Af-(benzyloxycarbonyl)-leucylleucic acid (Table 2) was prepared in 60% yield under the same conditions of addition using a 2 molar excess of pyridine to carbodiimide. 57 The DCC/pyridine technique was successfully utilized in the ring closure between ()-alanine and leucic acid residues during the synthesis of the cyclic hexadepsipeptide destruxin B.[58 Under this modified approach the... 

SCHEME 4.5 1,2-Migration in the stereoselective synthesis of 1, 2-tram (amino)-glyco-sides and 2-deoxyglycosides as reported by (a) Danishefsky, (b) Yu, and (c) Lowary. Ac, acetyl All, allyl Bn, benzyl Bz, benzoyl DTBMP, 2,6-di-fert-butyl-4-mcthyl pyridine TBDPS, ferf-butyldiphenylsilyl THF, tetrahydrofuran TIPS, triisopropylsilyl Tol, 4-tolyl. 

Tosyl chloride added to a stirred soln. of p-nitraniline in pyridine, and heated 30 min. on a steam bath under anhydrous conditions N-(p-nitrophenyl)-p-toluenesulfonamide (Y 95%) dissolved in dimethyl sulfoxide, treated with K-carbonate and 1,3-dibromopropane, stirred 5 days at room temp. N-(3-bromopropyl)-N-(p-nitrophenyl)-p-toluenesulfonamide (Y 80%) added to a mixture of ethyl acetoacetate, a 53.5%-dispersion of NaH in mineral oil, and ferf-butanol (previously warmed with stirring under anhydrous conditions until the NaH has dissolved and Hg-evolution ceased), refluxed 20 hrs. with stirring, and the resulting crude ethyl 2-acetyl-5-p-nitranilino)-N-(p-toluenesulfonyl)-valerate refluxed 48 hrs. with guanidine carbonate in ferf-butanol 2-amino-6-methyl-5- [ (N-p-toluenesulfonyl-p-nitranilino) propyl] -4-pyrimidinoI (Y 69%). F. e. s. B. R. Baker, D. V. Santi, and H. S. Shapiro, J. Pharm. Sci. 53, 1317 (1964). 

With educts containing an axially oriented LG at C-3, in addition to an intramolecular Sn2 reaction with an axially oriented hydroxy or acetamido group in a vicinal position (IS, Table 3, entries 1 [26] and 2 [30]), elimination and/or hydride shift (E or M/E, entries 3 [30],4 [31] and 6 [32]), as well as substitution with retention of configuration (AS, entries 7 and 8 [27b]) have been observed. For the transformation outhned in entry 4, 2,6-di-ferf-butyl-4-methylpyridine was used as acid scavenger, since pyridine per se in a similar reaction had caused Sn2 displacement (entry 5 [33]). Of special interest are the results from the deamination of methyl 3-amino-3-deoxy-/5-D-allopyranoside (entry 6), where the main reaction consists of direct Sn2 displacement with formation of methyl... 

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