Triethyl orthoformates synthesis

Fig. 2. Synthesis of uma2enil (18). The isonitrosoacetanihde is synthesized from 4-f1iioroani1ine. Cyclization using sulfuric acid is followed by oxidization using peracetic acid to the isatoic anhydride. Reaction of sarcosine in DMF and acetic acid leads to the benzodiazepine-2,5-dione. Deprotonation, phosphorylation, and subsequent reaction with diethyl malonate leads to the diester. After selective hydrolysis and decarboxylation the resulting monoester is nitrosated and catalyticaHy hydrogenated to the aminoester. Introduction of the final carbon atom is accompHshed by reaction of triethyl orthoformate to...

Although, 3-hydrazino[l,2,4]triazines have been shown to be versatile precursors for the synthesis of [l,2,4]triazolo[4,3-6][l,2,4]triazines, 3-hydrazino-l, 2,4-triazine-l-oxide 821 cyclized with triethyl orthoformate to give [l,2,4]triazolo[3,4-c][l,2,4]triazine 822. Cyclization takes place at N-4 of 821 (80JOC5421) (Scheme 166). 

The one-pot MCR of methylene active nitriles 47 has been used in the synthesis of both pyrano- and pyrido[2,3-d]pyrimidine-2,4-diones in a single-mode microwave reactor [90]. Microwave irradiation of either barbituric acids 61 or 6-amino- or 6-(hydroxyamino)uracils 62 with triethyl-orthoformate and nitriles 47 (Z = CN, C02Et) with acetic anhydride at 75 °C for 2-8 min gave pyrano- and pyrido[2,3-d]pyrimidines in excellent yield and also provided a direct route to pyrido[2,3-d]pyrimidine N-oxides (Scheme 27). 

A neat stereoselective synthesis of trans-fused tetrahydropyrano[3,2-c][l]benzopyrans involves treating salicylaldehydes with alk-4-en-l-ols and triethyl orthoformate. The selectivity is attributed to steric repulsion in the endo transition state, the precursor of the cw-fused compound <96CL889>. 

Nitroacetaldehyde diethyl acetal is prepared by the reaction of nitromethane with triethyl orthoformate in the presence of ZnCl2 (Eq. 5.8).17 Jager and coworkers have used this reagent for the synthesis of amino sugars via nitro-aldol reaction.18 Preparation of this useful reagent is now described in volume 74 of Organic Synthesis.19... 

A total synthesis of (35, 4/ )-(+)-eldanolide (246), a sex attractant pheromone, has been reported (243). Compound 246 was synthesized by two different routes, both involving the butenolide 245 as the key precursor. The higher-yielding sequence is described here. Treatment of the tosylate acetal 242 with methanolic sodium methoxide led, as previously described by Hoffman and Ladner (244), to the epoxide 243. Addition of lithium diiso-butenylcuprate to 243 afforded 244, which after successive hydrolysis of the isopropylidene group, treatment with triethyl orthoformate, and pyrolysis,... 

Synthesis of l-hydroxy-3-oxyimidazolines from a-hydroxylaminooximes has been reviewed " . Therefore, in the present work it will be described very briefly. In general, the reaction of oximes 136 with aldehydes, ketone or triethyl orthoformate leads to imidazolines 137 or 138, respectively (equation 60). 

All the syntheses of this type give piperid-4-ones or pyrid-4-ones. Errera reported that diethyl acetonedicarboxylate condensed with triethyl orthoformate in hot acetic anhydride, and that treatment of the product with ammonia gave a poor yield of the pyrid-4-one (644) (1898CB1682). It is certain that the intermediate is the di(ethoxyvinyl) ketone (643), so that this is perhaps better classified as a [5 + 1] synthesis, but most developments from this beginning do not involve isolation of intermediates. An arylamine has been used to obtain an A-arylpyrid-4-one (645) (46JA1253). 

The best route is the synthesis from ammonium acetate and triethyl orthoformate (see Section 2.20.4.5.2). 

A nitrile-stabilized carbanion is also involved in a synthesis of a fused pyranone system (81S225). A range of 2-ureidomethylenecyclohexane-l,3-diones, e.g. (308), react with activated acetonitriles in the presence of a strongly basic catalyst to produce 5-oxo-5,6,7,8-tetrahydrocoumarins (309). Since the substrates are readily available from cyclohexane-1,3-diones by reaction with triethyl orthoformate and a urea, the synthesis is attractive (Scheme 88). Furthermore, it has been applied to a pyran-2,4-dione, whereupon the 2,5-dioxopyrano[4,3-6]pyran (310) is formed. 

The same one-carbon unit has been employed in a convenient isoflavone synthesis from deoxybenzoins (76S326). Other methods of ring closure of phenyl benzyl ketones to this heterocycle have been reviewed (B-62MI22400) and include triethyl orthoformate (56PIA(A)(44)36), zinc cyanide (58CB2858), ethyl formate (80BCJ831) and ethoxalyl chloride (70JCS(C)1219). 

The hydrolysis of 4-alkoxybenzopyrylium salts leads to chromones in almost quantitative yields. The route is attractive because of the simple synthesis of the pyrylium salts (81CHE115). This method provides a reliable route to 3-substituted chromones, based on the reaction of 2-hydroxyphenacyl compounds with triethyl orthoformate. Furthermore, the use of triethyl orthoacetate enabled moderate yields of 2-methylchromones to be obtained <78JCR(M)0865). 

Neutral phosphates (RO)sPO, phosphonates (RO)2R PO and phosphinates (RO)R2PO are well known as extracting agents for metal ions.1823 The isolation of their metal complexes as crystalline compounds is, in general, more difficult than the preparation of complexes with other substituted phosphoryl compounds. It is often essential to reflux solutions of the reactants with dehydrating agents such as triethyl orthoformate or 2,2 -dimethoxypropane. In some cases the neutral phosphoryl ligands or triethyl orthoformate by themselves act as the reaction media in the synthesis of the nickel(II) complexes. 

The synthesis of dialkyl oxalates by oxycarbonylation of alcohols in the presence of a dehydrating agent and a Wacker catalyst was first reported by Fenton in 1968 (equation 177).378,449 As for the previous oxycarbonylations, the presence of water is a strong inhibitor of the reaction and favors the side-formation of C02 (equation 178). Dehydrating agents such as triethyl orthoformate or boric anhydride are necessary to prevent water formation and subsequent deactivation of the... 

A common approach to the synthesis of carbocyanine dyes, treatment of A-alkylazolium salts with triethyl orthoformate, has been used to obtain cyanines 20 containing the benzotellurazolium moiety (89KGS120). The long-wave absorption band in 20 is 52 nm bathochromically shifted relative to the corresponding sulfur analog. 

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