A de novo synthetic method to the access of N-substituted benzazepines

Selective Synthesis of Tetrahydroisoquinoline and Piperidine Scaffolds by Oxidative Ring Opening/Ring Closing Protocols of Substituted Indenes and Cyclopentenes

Novel tetrahydroisoquinoline and piperidine derivatives were selectively synthesized from substituted indenes or cyclopentenes. The process starts with an oxidative cleavage of the ring olefin bond, which gives reactive diformyl intermediates. By a ring-closing step using chiral (R) or (S) α-methylbenzylamine under a reductive amination protocol facilitated ring formation with ring expansion of the corresponding nitrogen-containing heterocycles. The stereocontrolled methodology enabled accurate control of the stereochemistry of the final products. Additionally, the synthesized amino acid derivatives possessing an aryl moiety in their structure may be relevant building blocks for foldamer chemistry.

Application of Oxidative Ring Opening/Ring Closing by Reductive Amination Protocol for the Stereocontrolled Synthesis of Functionalized Azaheterocycles

The current Account gives an insight into the synthesis of some N-heterocyclic β-amino acid derivatives and various functionalized saturated azaheterocycles accessed from substituted cycloalkenes via ring C=C bond oxidative cleavage followed by ring closing across double reductive amination. The ring-cleavage protocol has been accomplished according to two common approaches: a) Os-catalyzed dihydroxylation/NaIO4 vicinal diol oxidation and b) ozonolysis. A comparative study on these methodologies has been investigated. Due to the everincreasing relevance of organofluorine chemistry in drug research as well as of the high biological potential of β-amino acid derivatives several illustrative examples to the access of various fluorine-containing piperidine or azepane β-amino acid derivatives are also presented in the current Account.

1 Introduction

2 Olefin-Bond Transformation by Oxidative Ring Cleavage

3 Synthesis of Saturated Azaheterocycles via Oxidative Ring-Opening/Ring-Closing Double Reductive Amination

3.1 Importance of Fluorine-Containing Azaheterocycles in Pharmaceutical Research

3.2 Synthesis of Azaheterocyclic Amino Acid Derivatives with a Piperidine or Azepane Framework through Oxidative Ring Opening/Reductive Amination

3.2.1 Synthesis of Piperidine β-Amino Esters

3.2.2 Synthesis of Azepane β-Amino Esters

3.2.3 Synthesis of Fluorine-Containing Piperidine γ-Amino Esters

3.3 Synthesis of Tetrahydroisoquinoline Derivatives through Oxidative Ring Opening/Reductive Amination Protocol

3.4 Synthesis of Functionalized Benzazepines through Reductive Amination

3.4.1 Synthesis of Benzo[c]azepines

3.4.2 Synthesis of Benzo[d]azepines

3.5 Synthesis of Various N-Heterocycles via Ozonolysis/Reductive Amination

3.5.1 Synthesis of Compounds with an Azepane Ring

3.5.2 Synthesis of Piperidine β-Amino Acids and Piperidine-Fused β-Lactams

3.5.3 Synthesis of γ-Lactams with a Piperidine Ring

3.5.4 Synthesis of other N-Heterocycles

4 Summary and Outlook

5 List of Abbreviations