4 -Quinazolinones preparation

Quinazolinones are an important class of fused heterocycles that have been reported with remarkable activities in biology and pharmacology such as anticancer, antiinflammatory, anticonvulsant, antibacterial, antidiabetic, hypolipidemic, and protein tyrosine kinase inhibitors. Alper and Zheng reported a palladium-catalyzed cyclocarbonylation of o-iodoanilines with imidoyl chlorides to produce quinazolin-4(3H)-ones in 2008. A wide variety of substituted quinazolin-4(3H)-ones were prepared in 63-91% yields (Scheme 3.27a). The reaction is believed to proceed via in situ formation of an amidine, followed by oxidative addition, CO insertion, and intramolecular cyclization to give the substituted quinazolin-4(3H)-ones. Later on, a procedure was established based on generating the amidine in situ by a copper-catalyzed reaction of terminal allq nes, sulfonyl azide and o-iodo-anilines. The desired quinazolinones can be produced by carbonylation with Pd(OAc)2-DPPB-NEt3-THF as the reaction system. In the same year, Alper s group developed a procedure for 2,3-dihydro-4(lH)-quinazolinone preparation. The reaction started with the reaction of 2-iodoanilines and N-toluenesulfonyl aldimines followed by palladium-catalyzed intramolecular... 

Methyl-4-hydroxyquinazoline reacts with organic halides, in the presence of sodium methoxide, to give 3-substituted 2-methyl-4(3i/)-quinazolinones. The 0-acetyl derivative of 4-hydroxyquinazoline has been prepared under anhydrous conditions and gives the hydroxy compound with water or with lithium aluminum hydride. The N-3 acetyl derivative, however, is more stable and gives 3-methyl-4(31/)-quinazolinone with lithium aluminum hydride. ... 

Methylation of hydroxyquinazolines invariably produces a mixture of 0- and A -methylated derivatives. The A -methyl derivatives are, therefore, best prepared by unequivocal syntheses. 1-Methyl-2(1H)-quinazolinone (16) is not known. When o-aminobenzaldehyde is treated with methylisocyanate, 3-methyl-2(3i7)quinazolinone (17) is obtained. If this is heated in ethanol it dissolves and an alcoholate, presumably (18), crystallizes out, and this can be converted back to (17) by vacuum sublimation. Methylation of l-methyl-4(lH)Quinaz-... 

Substituted 2-mercapto-4(3i/)quinazolinones were prepared by condensing methyl anthranilate with isothiocyanates (see 7c). 

Reaction of malononitrile and quinazolinone 429 in the presence of three drops of NEts yielded pyrido[2,l-Z)]quinazolinone 430 (97MI7). 9,11-Dioxo-5,9-dihydro-l l//-pyrido[2,l-Z)]quinoline-8-carboxylates 432 were prepared in the reaction of anthranilonitrile and 2-piperidones 431 in boiling EtOH in the presence of AcOH (00JCS(P1)3686, 00PS133). 

Fluproquazone (97) contains a 2-quinazolinone nucleus and is found to be an analgetic agent useful in mild to moderate pain. One of the preparations involves reaetion of 2-isopropylamino-4-methyl-4 -fluoro-benzophenone (96) with potassium cyanate in hot acetic acid [27],... 

Ring-opening of diastereomerically pure vinylaziridine 131, prepared by azir-idination of butadiene with 3-acetoxyaminoquinazolinone 130 [52], yielded acetate 132 with inversion of configuration, together with amino alcohol 133 with retention (Scheme 2.34) [53]. The formation of 133 can be explained by assuming participation by the quinazolinone carbonyl oxygen, which produces an intramolecular reaction with the aziridine carbon with retention of configuration. 

The 2-aminoquinazolines 259 were prepared in two independent ways. The 2-quinazolinone 258 was transformed to 2-aminoquinazoline 259 by treatment with phosphorus oxychloride and subsequently with sodium amide in liquid ammonia, or with phosphorus pentachloride under carefully controlled conditions [75JCS(P1)1471]. Attempts to prepare the N-substituted derivatives failed, but the reaction was successful with the unsubstituted cis cyclopentane-fused homolog [76JCS(P1)1415]. 

A great number of 4-oxopyrimidines have been prepared by cyclization of )8-amino acid derivatives with oxo reagents. All the compounds discussed here involve cyclohexane ring fusion, and therefore the quinazolinone nomenclature can be used. 

The diendo- and diexo-norbornane- and norbornene-fused quinazolinones 272 and 273 were prepared from the corresponding carboxamides and 4-chlorobenzaldehyde (87CB259). 

The synthesis of oxaziridine-fused quinazolinones 277 follows a different route. Quinazolinones 274 (R = Et, nPr, n-hexyl) can readily be prepared by reacting 2-oxo-l-cyclohexanecarboxamide with aldehydes in the presence of ammonia solution. In the reaction of 274 and monoperoxyphthalic acid, the hydroxyoxaziridines 277 were formed via the presumed intermediates 275 and 276. No spectroscopic evidence was given for 277, nor was its relative configuration investigated [76JPR(318)895]. 

Thioquinazolincs can also be prepared by the reaction of lithiated quinazoline derivatives with disulfides. For example, reaction of the lithio species derived from 6-bromo-4(3//)-quinazolinone 74 with tetra-iso-propylthiuram disulfide gave the 6-dithiocarbamate 75 in 81% yield <2004M323>. 

Z- and 4-alkoxyquinazolines are readily prepared by nucleophilic substitution reactions, and 2,4-dialkoxyquinazolines can simply be prepared by boiling 2,4-dichloroquinazolines with 2 equiv of an alkoxide in the appropriate alcohol solvent <1996HC(55)1>. The first substitution is in the more reactive 4-position, so it is possible to isolate both 4-alkoxy and 4-phenoxy monosubstitution products <1977EJM325, 2005BMC3681>, and this selectivity has been used to attach both 2,4,6- and 2,4,7-trichloroquinazoline to a solid support, via the 4-position, for subsequent solid-phase synthesis of 2,6- and 2,7-diamino-4(377)-quinazolinones <2003TL7533>. 

The pattern of organometallic addition to quinazolinones follows that for the quinazolines, with both 4(377)-quinazolinones 434 (X = O) and 4(377)-quinazolinethiones 434 (X = S) undergoing addition at the 2-position. Both 3-unsubstituted (R = H) and 3-acylamino (R =MeCONH or /-BuCONFl) derivatives 435 have been prepared <1996JOC656, 2004M323, 2005JSF121>. 

The above two quinazolinones were prepared as intermediates in the synthesis of the chiral nonnucleoside reverse transcriptase inhibitor DPC 961 441, although compounds of this type can also be formed directly by the addition of lithium cyclopropylacetylide to the N-unsubstituted 2(l//)-quinazolinone 440, in the presence of a chiral alkoxide moderator <20000L3119, 2004JA5427>. 

Alkenyl quinazolinone derivatives can also be prepared under Lewis acid conditions, as demonstrated by the synthesis of analogs of the anticonvulsant piriqualone 574, where aldehyde condensation and elimination of water was conveniently effected with zinc chloride and acetic anhydride <2001BML177>. 

Due to the electron-withdrawing nature of the pyrimidine ring, alkenylpyrimidines can undergo addition reactions at the /3-carbon, and while this is a well-established route to substituted pyrimidine derivatives <1994HC(52)1, 1996CHEC-II(6)93>, it has also been used to prepare quinazolinone derivatives 578 from 2-alkenyM(3//)-quinazo-linones 577 <2000T7245>. 

A -Benzyl groups on pyrimidinones and quinazolinones are removable by hydrogenolysis, although it is now more common to use a PMB substituent that can be removed with either TFA or CAN. Other N-protecting groups to be commonly used include benzyloxymethyl (BOM), removable by hydrogenation, ferZ-butoxycarbonyl (BOC), removable by anhydrous acid, and pivaloyloxymethyl (POM), which is removable by methanolic ammonia at room temperature. Alkenyl pyrimidinones have been employed in 1,3-dipolar cycloaddition reactions to prepare heterocyclic nucleotides. 

An alternative procedure, using sulfuric acid on silica as the catalyst, under solvent-free conditions, gave similar products, and 3-unsubstituted 4(3//)-quinazolinones 893 could also be prepared using ammonium acetate as the amine source <2005TL7051>. 

The usual precursor is an appropriately orf/to-disubstituted benzene. Thus, quinazolines (290) can be prepared by the reaction of o-acylanilines (289 R = alkyl) with amides RCONH2. Heating anthranilic acid (289 R = OH) with amides or amidines yields 4-quinazolinones (291). The second nitrogen can be introduced into (289) before ring closure, as in (292) + HC(OEt)3 — (293). 

Numerous solid-phase preparations of quinazolinones have been reported. The main synthetic strategies used are summarized in Figure 15.16. Quinazolin-2,4-diones can be prepared from anthranilic acid derived ureas or from N-(alkoxycarbonyl)-anthranilamides. These reactions have been performed on insoluble supports either in such a way that the cyclized product remains linked to the support, or such that it is simultaneously cleaved from the support upon ring formation. Quinazolin-4-ones can be prepared by cyclocondensation of anthranilamides with aldehydes, orthoesters [342], or other carboxylic acid derivatives [343]. The selection of examples listed in Table 15.29 illustrates the variety of substitution patterns accessible by means of these cyclizations. 

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