Synthesis of lactams and other nitrogen heterocycles by intramolecular cyclizations of carbamates and acyl derivatives of aminosulfones

Type 1 Ring-Opening Reactions of Cyclopropanated 7-Azabenzonorbornadienes with Organocuprates

The first nucleophilic ring-opening reactions of cyclopropanated 7-azabenzonorbornadienes have been achieved using organocuprates. Tricyclic or tetracyclic γ-lactams were obtained as the sole product in good yields of up to 98% when alkoxycarbonyl groups occupied the N-substituent position. Successful conversions to lactams were observed for primary, secondary, tertiary, and aromatic nucleophiles, as well as for a variety of substrates functionalized on the benzene ring. A possible mechanism for these transformations is discussed.

A new approach to cyclic hydroxamic acids: Intramolecular cyclization of N-benzyloxy carbamates with carbon nucleophiles

N-Alkyl-N-benzyloxy carbamates, 2, undergo facile intramolecular cyclization with a variety of carbon nucleophiles to give functionalized 5- and 6-membered protected cyclic hydroxamic acids, 3, in good to excellent yields. This method can be extended to prepare seven-membered cyclic hydroxamic acids in moderate yields. The sulfone intermediates 3 from this study can be alkylated while the corresponding phosphonates have been shown to undergo HWE reaction. The α,β-unsaturated synthon, 8, prepared by thermal elimination of sulfoxide 3m, undergoes Michael addition with secondary amines. The usefulness of this approach to prepare polydentate chelators has been demonstrated by the synthesis of bis cyclic hydroxamic acids 12, 14, and 15.

Chiral oxazolidinones as electrophiles: Intramolecular cyclization reactions with carbanions and preparation of functionalized lactams

The intramolecular cyclizations of oxazolidinones with carbanions adjacent to sulfones, sulfoxides and phosphonates proceed in high yields to obtain functionalized γ and δ lactams. The chiral oxazolidinone precursors can be readily synthesized from commercial amino acids. The lactams from this study are useful synthetic intermediates, as demonstrated by the synthesis of a precursor for levetiracetam, an antiepileptic drug.

Reactions of N-benzyloxycarbamate derivatives with stabilized carbon nucleophiles: a new synthetic approach to polyhydroxamic acids and other hydroxamate-containing mixed ligand systems

Hydroxamic acids are an important class of chelators of hard metal ions such as Fe(III), which have found applications in therapeutic, diagnostic, and separation chemistry. Hence, methods for their preparation and incorporation into various matrices are important. A new strategy for the preparation of hydroxamic acids that uses readily available N-benzyloxy carbamic acid ethyl ester, 1, has been developed. N-Alkylation of 1 occurs readily to give N-alkyl-N-benzyloxy carbamates, 2, which react with a variety of stabilized carbon nucleophiles to give functionalized protected hydroxamic acids, 3, in good to excellent yields. The O-protected hydroxamate intermediates 3 can be further alkylated with halides to access a variety of potential metal binding hosts. The usefulness of this methodology has been demonstrated by the synthesis of a novel trihydroxamic acid 6, mixed ligand systems 9 and 12, and the macrocyclic dihydroxamic acid 16.