260-32-2

Usage

Synthesis Reference(s)

The Journal of Organic Chemistry, 50, p. 2746, 1985 DOI: 10.1021/jo00215a031

Upstream product

• 108-99-6 3-Methylpyridine 
• 100-44-7 benzyl chloride 
• 138823-83-3 4-Benzyl-pyridine-3-carbaldehyde 
• 66-99-9 β-naphthaldehyde 
• 96913-99-4 5,10-dihydro-5,10-epoxybenzisoquinoline 
• 36995-46-7 4-[(2-methylphenyl)methyl]pyridine 

Downstream Products

• 46492-08-4 benz[g]isoquinoline-5,10-dione 
• 75052-15-2 2-phenacylbenzoisoquinolinium bromide 
• 75061-08-4 3-benzoyl-1,2-dicarbomethoxynaphth<2,3-g>indolizine 
• 75052-20-9 benzoisoquinolinium dibenzoylmethylid 
• 75052-17-4 benzoisoquinolinium benzoylmethylid 

Relevant academic research and scientific papers

Rh-Catalyzed Ortho C-H Alkynylation of Aromatic Aldehydes

The Rh(III)-catalyzed ortho-alkynylation of benzaldehydes is enabled by the transient formation of an imine as a directing group. A broad scope of substrates was obtained under mild reaction conditions, granting access to mono- and dialkynylated products. The functionalization of readily available building blocks allowed the development of modular syntheses of dibenzopentalenes, isoquinolines, indoles, and indolines.

General synthetic route to benz[g]isoquinolines (2-azaanthracenes)

Benzylic zinc reagents add with high regioselectivity to 1- (phenoxycarbonyl) salts derived from pyridine-3-carboxaldehyde (1a) or 3- acetylpyridine (b) to yield 1-(phenoxylcarbonyl)-4-benzyl-1,4- dihydropyridine-3-carboxaldehydes 5a, 5c or ketones 5b, 5d. Aromatizations of these dihydro analogues with sulfur led to the corresponding aldehydes 6a, 6c or ketones 6b, 6d. An alternate synthesis to the aldehydic precursors involved additions of benzylic zinc reagents to 1-(phenoxycarbonyl) salts formed from methyl nicotinates which led to the corresponding methyl 1- (phenoxycarbonyl)-4-benzyl-1,4-dihydronicotinates 7a, 7b. Aromatizations of 7a, 7b led to the corresponding pyridine esters 8a, 8b which on reduction with lithium aluminum hydride yielded the corresponding carbinols 9a, 9b. Oxidation of 9a, 9b by manganese dioxide afforded aldehydes 6e, 6f. Aldehydes 6a-f were readily converted into the benz[g]isoquinolines 10a-f on heating in polyphosphoric acid.

Preparation of Isobenzofuran-Aryne Cycloadducts

A one-pot procedure is described for carrying out the sequence 1,4-elimination of acetal 1 to form isobenzofuran; the formation of 1,3-dilithioisobenzofuran; the conversion to 1,3-bis(trimethylsilyl)isobenzofuran (5); the generation of arynes and cycloaddition to 5.This method allows the use of lithium tetramethylpiperidide induced dehydrohalogenation of haloaromatics to generate the arynes, a procedure which fails with unsilylated isobenzofuran due to the acidity of the 1,3-protons.The protiodesilylation of the cycloadducts occurs with surprising ease, upon treatmentwith either tetraalkylammonium fluoride/THF or base (potassium tert-butoxide or KOH) in Me2SO, to furnish the novel unsubstituted isobenzofuran-aryne adducts.Three examples are given, utilizing benzyne, 1-naphthalyne, and 3-pyridine.Procedures for subsequent deoxygenation of the cycloadducts to anthracene, benzanthracene, and benzisoquinoline, respectively, are described.The cycloadduct precursor of benzanthracene is shown to undergo highly regioselective reduction on treatment with lithium tri-tert-butoxyaluminohydride/triethylborane, with preferential attack occurring at the more accessible 7-position.

SUBSTITUTED 2- AND 4-BENZYLPYRIDINES IN THE SYNTHESIS OF BENZOQUINOLINES AND BENZOISOQUINOLINES

Nitrogen-containing heterocyclic analogs of anthracene, viz., benzoisoquinolines and benzoquinolines, were obtained by dehydrocyclization on a K-16 catalyst of mixtures of methyl-substituted 2- and 4-benzylpyridines with methyl groups in various positions of the pyridine and benzyl rings, which are formed by benzylation of β-picoline, as well as pyridine, by the Ladenburg method.The spectral characteristics of the synthesized compounds are presented.