Reactions of [2‐(2‐Naphthyl)phenyl]acetylenes and 2‐(2‐Naphthyl)benzaldehyde O‐Phenyloximes: Synthesis of the Angucycline Tetrangulol and 1, 10, 12‐Trimethoxy‐8‐methylbenzo[c]phenanthridine. Issue 11 (21st March 2017)

• Record Type: Journal Article
• Authors: Ngwira, Kennedy J.; Rousseau, Amanda L.; Johnson, Myron M.; de Koning, Charles B.
• Is Part Of: European journal of organic chemistry. Issue 11(2017)
• Page Start: 1479
• Page End: 1488
• Publication Date: 2017-03-21
• Subjects: Natural products -- Total synthesis -- Cross‐coupling -- Platinum -- Cyclization; Chemistry, Organic -- Periodicals; Organic compounds -- Synthesis -- Periodicals; Bioorganic chemistry -- Periodicals; Chemistry, Physical organic -- Periodicals; 547
• DOI: 10.1002/ejoc.201601373
• Languages: English
• ISSNs: 1434-193X

Abstract

Abstract : The Suzuki–Miyaura coupling reaction between (1, 4, 5‐trimethoxynaphthalen‐2‐yl)boronic acid and 2‐iodo‐3‐methoxy‐5‐methylbenzaldehyde gave the intermediate 3‐methoxy‐5‐methyl‐2‐(1, 4, 5‐trimethoxynaphthalen‐2‐yl)benzaldehyde. Conversion of this benzaldehyde into the alkyne 2‐(2‐ethynyl‐6‐methoxy‐4‐methylphenyl)‐1, 4, 5‐trimethoxynaphthalene was accomplished through a Corey–Fuchs reaction. Exposure of the derived acetylene to a catalytic platinum(II)‐mediated ring closure gave the required tetracyclic aromatic product, 1, 7, 8, 12‐tetramethoxy‐3‐methyltetraphene, which was then converted into tetrangulol. Exposure of the related 3‐methoxy‐5‐methyl‐2‐(1, 4, 5‐trimethoxynaphthalen‐2‐yl)benzaldehyde O ‐phenyloxime to microwave irradiation in an ionic liquid yielded 1, 10, 12‐trimethoxy‐8‐methylbenzo[ c ]phenanthridine, instead of the desired natural product phenanthroviridone. Abstract : Cycloisomerization of a biarylylalkyne in the presence of catalytic PtCl2 resulted in the formation of 1, 7, 8, 12‐tetramethoxy‐3‐methyltetraphene, which was easily converted into the natural product tetrangulol.