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The 14-membered macrocycles representing the F-O-G ring of teicoplanin are prepared by an intramolecular S(sub N)Ar reaction involving macrocyclization through the generation of biaryl ether. During the macrocyclization reaction, ortho and para nitro fluoro disubstituted aromatic rings and tethered aryl oxides are used. Fluoride in milder conditions is used as the leaving fragment in the reaction.

Use of intramolecular SNAr reaction helps prepare 16-membered macrocyclic COD and DOE rings related to the vancomycin family of glycopeptides. Mild conditions employed in the reaction prevent racemization even on introducing a racemization-prone amino acid into the acyclic chain. The advantage of this method is that it permits the introduction of a chlorine or hydrogen atom, thus achieving the substitution patterns present in the vancomycin family of glycopeptides.

Selective three‐component 1,2‐diamination of 1,3‐dienes with concurrent introduction of two orthogonally protected amino groups remains unknown despite its significant synthetic potential. We report herein that reaction of conjugated dienes with N‐aminopyridinium salts and TMSNCS affords 1,2‐aminoisothiocyanation products in a highly chemo‐ and regio‐selective manner under mild photoredox catalytic conditions. Mechanistic studies indicate that the facile isomerization of allyl thiocyanates to allyl isothiocyanates under photocatalytic conditions is responsible for the selective formation of the observed products. The mild isomerization protocol is expected to find applications in the synthesis of allyl isothiocyanates in a broad sense. [ABSTRACT FROM AUTHOR]

2,3,3‐Trisubstituted indolenine constitutes an integral part of many biologically important monoterpene indole alkaloids. We report herein an unprecedented access to this skeleton by a TiCl3‐mediated reductive cyclization of tetrasubstituted alkenes bearing a 2‐nitrophenyl substituent. The proof of concept is demonstrated firstly by accomplishing a concise total synthesis of (+)‐1,2‐dehydroaspidospermidine featuring a late‐stage application of this key transformation. A sequence of reduction of nitroarene to nitrosoarene followed by 6π‐electron‐5‐atom electrocyclization and a 1,2‐alkyl shift of the resulting nitrone intermediate was proposed to account for the reaction outcome. A subsequent total synthesis of (+)‐condyfoline not only illustrates the generality of the reaction, but also provides a mechanistic insight into the nature of the 1,2‐alkyl shift. The exclusive formation of (+)‐condyfoline indicates that the 1,2‐alkyl migration follows a concerted Wagner–Meerwein pathway, rather than a stepwise retro‐Mannich/Mannich reaction sequence. Conditions for almost quantitative conversion of (+)‐condyfoline to (−)‐tubifoline by way of a retro‐Mannich/1,3‐prototropy/transannular cyclization cascade are also documented. [ABSTRACT FROM AUTHOR]

We report herein a synthesis of 5,6‐diarylbenzo[a]carbazoles by a sequence of 6π‐electrocyclization followed by β‐elimination. The highly functionalized 2,3‐disubstituted indoles used for this cycloaromatization process are prepared by Pd‐catalyzed cyclizative cross‐coupling of ortho‐alkynylanilines with ortho‐alkynylbenzamides. The combination of these two reactions allows us to develop a facile synthesis of benzo[a]carbazoles directly from two easily accessible internal alkynes without isolation of the indole intermediates. [ABSTRACT FROM AUTHOR]

We report in this article a cascade reaction strategy for the synthesis of complex N‐heterocyclic compounds with contiguous and tetrasubstituted stereogenic carbons. Under the sequential catalysis of a chiral binol–Ti complex and BF3, cyclopentanone‐derived tertiary enamides undergo an enantioselective enamine addition to ketone carbonyls followed by diastereoselective trapping of the resulting acyliminiums by electron‐rich aryl moieties to furnish four‐ and five‐membered ring‐fused N‐heterocyclic products as the sole diastereomers in high yields with up to 99 % ee. [ABSTRACT FROM AUTHOR]

We report in this paper a novel Cu‐catalyzed synthesis of polysubstituted 1‐pyrrolines. The reaction of β,γ‐unsaturated oxime esters 4 with terminal alkynes 5 in the presence of a catalytic amount of Cu(OAc)2 and 2,2′‐biquinoline affords the corresponding 1,6‐enynimines, which undergo a highly stereoselective Alder‐ene reaction to afford 1‐pyrrolines with concomitant generation of a quaternary carbon and a 2‐azadiene motif. It represents an unusual [4+1] heteroannulation reaction wherein terminal alkynes act as a one carbon donor and are 1,1‐difunctionalized. Mechanistic studies suggest that the allylic hydrogen trans to the oxime ester main chain is selectively transferred to the electron‐rich alkyne during the pericyclic reaction. The resulting 1‐pyrrolines undergo facile acid‐catalyzed regioselective Wagner–Meerwein rearrangement to provide 2H‐pyrroles in excellent yields. The 2H‐pyrroles are also accessible from 4 and 5 in a one‐pot manner without isolation of the 1‐pyrrolines. Leveraging this heteroannulation reaction as a key step, the first total synthesis of borrecapine, a 2,3,3,5‐tetrasubstituted pyrrolidine, is accomplished. [ABSTRACT FROM AUTHOR]

A new synthesis of highly functionalized cyclic sugar amino acids that allow to access macrocycles in two steps from simple starting materials is reported. In this two-step process only two molecules of water are lost and lithium hydroxide and trifluoroacetic acid reagents are used to mediate the formation of these macrocycles.