Reactivity of Substituents Attached to Ring Heteroatoms

Reactions of substituents attached to ring heteroatoms have been studied only on 1,4-dihetero-pentalene systems, mainly furo[3,2-6]pyrrole derivatives. 

The acetyl group of the 4-acetylfuro[3,2-6]pyrrole (8b) (see Table 6) readily undergoes hydrolysis and under conditions of phase transfer catalysis with methyl iodide or benzyl chloride gave the 4-methyl (8c) or 4-benzylfuro[3,2-6]pyrrole (8d) via the unstable 4//-furo[3,2-6]pyrrole (8) 92CCC1487 . 

The reaction of ethyl 2-phenyl-4//-furo[3,2-/ ]pyrrole-5-carboxylate (94) with 2-nitrobenzyl-oromide afforded ethyl 4-(2-nitrobenzyl)-2-phenylfuro[3,2-6]pyrrole-5-carboxylate (269) under conditions of phase transfer catalysis by utilization of sodium carbonate and tetrabutylammonium bromide. This product (269) was hydrogenated using palladium-on-charcoal catalyst to give the amine (270), which cyclized in the presence of 2-hydroxypyridine to give 2-phenylfuro[2, 3 4,5]pyrrolo[2,l-c]benzo[l,4]diazepin-l 1-one (271) 92CCC1487 . 

8 Reactivity of Substituents Attached to Ring Heteroatoms 12.01.8.1 Rearrangements in A/-Allylquinolizinium Derivatives 

Some reactions of the substituents attached to ring heteroatoms have been partly described in CHEC-II(1996) 1996CHEC-II(7)1 . 

It was found that the order of reactions could be reversed, with the nitrogen alkylation performed prior to the Suzuki reaction. In that way, compounds 340a and 340b were synthesized in 79% and 78% yields, respectively. The synthesis of compounds 341-343 was also described 2003TL4257 . 

Numerous publications have been devoted to the reactions of substituents attached to the nitrogen atoms of 1,2,3-triazoles, and particularly of benzotriazoles. Several comprehensive reviews have appeared 91X2683, 94M1 401-01, 94S445 . 

1 Reactivity of A amino, A hydroxy, V-nitro and A -cyano Substituents 

For a review of V-amino-l,2,3-triazoles, see Kuzmenko and Pozharskii 92AHC(53)85 . For the oxidation of iV-aminotriazoles and benzotriazoles, also see Section 4.01.4.11. 

Sodium imidazolate (Naim), sodium cyanide, and other reagents smoothly deacetylate the cyclic 2,3-sulfamidate 126 (Equation 32) 1997T5863 . 

Removal of the / -methoxybenzoyl (PMB) group in sulfamide (Equation 33) 20010L405 . 124 was effected with ceric ammonium nitrate 

Deprotection of the tert-butoxycarbonyl- (BOC) and dibenzosuberyl- (Sub) substituted sulfamidates 142 was readily accomplished at room temperature with an excess of trifluoroacetic acid in CH2C12 (Equation 34) 2002JOC5164 . 

9 Ring Syntheses from Acyclic Compounds Classified by Number of Ring Atoms Contributed by Each Component 

Much attention was given in CHEC-II(1996) 1996CHEC-II(4)409 to the synthesis of 1,2,3-dithiazoles. Cyclic and acyclic oximes were found to be important precursors to their preparation. The discovery of 4,5-dichloro-1,2,3-dithiazolium chloride (Appel salt 20) from the reaction of commercial and cheap acetonitrile and disulfur dichloride gave strong impulse to the synthesis of various 1,2,3-dithiazole derivatives. Formation of the 1,2,3-oxathiazole ring involved almost exclusively the conversion of m -aminohydroxyl compounds to the A-oxide derivatives. 

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Reactivity of substituents attached to ring heteroatoms has not been reported. 

Reactivity of substituents attached to ring heteroatoms 5.2.2.7 Alkyl groups and further carbon functional groups. The N-2-nitrobenzoyl derivative of indolo benzazepine 384a can be easily deprotected on the indole nitrogen by treatment with N,N-diethylaminoethylamine in DMF at room temperature (Scheme 79, Section 5.1.2 (1991JHC379)). 

REACTIVITY OF SUBSTITUENTS ATTACHED TO RING HETEROATOMS 4.09.8.1 N-linked Substituents... 

There are no reports concerning reactivity of substituents attached to ring heteroatoms. In fact, most 1,4-(oxa/thia)-2-azoles are unsubstituted at ring heteroatoms and the only data concerning dithia- or oxathiazolidine S,S-dioxides, or N-substituted derivatives is limited to their preparation and to the reactivity of the ring systems. 

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