Tetrahydro preparation

The procedure described is essentially that of Richet which has been repeated. The reaction is of interest since it provides a facile method of preparing tetrahydro-3-furanones which are useful reagents for alkylation in the Friedel-Crafts reaction. ... 

A new method of preparing tetrahydro-1,3-oxazine derivatives (13 and 14) consists in reacting olefins with formaldehyde and ammonium chloride or hydrochlorides of primary amines. ... 

In addition to the dihydro compounds discussed above, the triethylsilane/trifluoroacetic acid reduction system can also be used to prepare tetrahydro pyrimidine derivatives, especially when dichloromethane is used as the solvent <2004TL2107>. Thus, treatment of 2-amino-5-phenylpyrimidine 398 with 2.5 equiv of triethylsilane and 5 equiv of TEA in dichloromethane at room temperature gave a quantitative yield of the tetrahydro derivative 399, whereas only a dihydro derivative was obtained with 10 equiv of the silane in the absence of dichloromethane <2004TL2107>. 

Hosami and co-workers (12,173,174) prepared alternative forms of nonstabilized ylides (Scheme 4.87). They generated tailor-made carbonyl ylides from substituted 1,3-dichloroethers through a 1,3-elimination pathway mediated with a samarium reagent. These simple carbonyl ylide intermediates are valuable for preparing tetrahydro- and dihydrofurans. To a mixture of bis(chloromethyl) ethers and... 

So far there are only four known methods for preparing tetrahydro-l,2,3,4-tetrazines. The method which gives the best yields of the 1,4,5,6-tetrahydro compounds is that from a-lithiated iV-alkylnitrosamines (19). These compounds decompose at -73 °C to yield the 1,4,5,6-tetrahydrotetrazine 2-oxides (5) which can be reduced by trimethyl phosphite or lithium aluminum hydride to the l,4(5,6-tetrahydro-l,2,3,4-tetrazines (11) (73AG504, 74GEP2327545, 78HCA1622). 

Beams and Manders reported (177) the synthesis of the tricyclic dione 349 via two different synthetic routes. The Australian chemists utilized an approach analogous to one developed earlier by Masamune (178) during the synthesis of atisine and kaurene. They prepared tetrahydro-7-methoxy-2-naphthoic acid (350) from 7-methoxytetral-l-one by published procedures. 

Many workers have employed j3-halocarboxylic acids (142) to prepare tetrahydro-l,3-thiazines (143) from thioureas. The halogen atom (X)... 

The acid-catalyzed Pictet-Spengler reaction between tryptamine derivatives and aldehydes is a well-established method for preparing tetrahydro-p-carboline (THpC) derivatives." Our first trials were aimed at using the bisnlfite adduct as the carbonyl sonrce in order to minimize the number of process steps. The reaction was performed by reacting the 5-methyltryptamine hydrochloride with an excess (1.3 eqniv) of the sodium bisulfite adduct in EtOH at reflnx, in the presence of one extra eqnivalent of HCl. The rac-THpC was simply isolated as a hydrochloride salt by filtration of the reaction mixture (Scheme 6.8). 

A three component condensation involving aryl amines, aldehydes, and olefins was used to assemble a variety of tetrahydroquinolines [83]. Dihydropyrimidine-2,4-diones were prepared from condensing amines with resin bound acrylates followed by treatment with isocyanates [84]. Two additional groups have published their work using the Pictet-Spengler reaction to prepare tetrahydro- -carbolines [85], tetrahydroisoquinolines [86] and... 

Propylene Urea Resins. In similat fashion to ethyleneurea, dimethyl-olpropyleneurea [3270-74-4] [l,3-bis(hydroxymethyl)tetrahydro-2-(m)-pyrimidinone] is the basis of propyleneurea—formaldehyde resin [65405-39-2], Its preparation is from urea, 1,3-diaminoptopane [109-76-2] and formaldehyde. 

The reaction of vinylogous amides, or ketoaldehydes, with hydroxylamine produced 4,5,6,7-tetrahydro-l,2-benzisoxazole. A side product is the 2,1-benzisoxazole (Scheme 173) (67AHC(8)277). The ring system can also be prepared by the reaction of cyclohexanone enamines with nitrile oxides (Scheme 173) (78S43, 74KGS901). Base treatment produced ring fission products and photolysis resulted in isomerization to benzoxazoles (76JOC13). 

Benzo[b]thiophenium, 1,2,3,5-tetramethyl-theoretical methods, 4, 3 Benzo[b]thiophenium salts preparation, 4, 723-724 Ben2o[b]thiophen-4-one, 4,5,6,7-tetrahydro-synthesis, 4, 905-906 5H-Benzo[b]thiophen-4-one, 6,7-dihydro-synthesis, 4, 900 Benzo[b]thiophyne, 4, 750 1H- 1,3,4-Benzotriazepine, 2,3-dihydro-synthesis, 7, 637 1H-1,2,4-Benzotriazepines synthesis, 7, 638 1,2,5-Benzotriazepines synthesis, 7, 640... 

Carbethoxy)-3-rnethyl-3,4,5,6-tetrahydrO 2H-pentalen-l-one (2). A solution of ethyl 2-ethytidene-3-(1-cyclopenten-1-yl)-3-oxo-propanoate 1 (210 mg. 1 mmol) in CH2CI2 (10 mL) was stirred with SnCU (780 mg, 3 mmol) lor 24 h at 20°C After quenching with water (50 mL), the organic layer was washed (N3HCO3), dned (UgS04) and punlied by preparative TLC to afford 62 5 mg of 2 (30%)... 

Of more direct interest is the preparation of 3-ethylquinuclidine by this method (Prelog, Sogtaric and Gustak (1940)). Ethyl tetrahydropyranyl ketone (X R = tetrahydropyranyl in X to XIV) was condensed wiA ethyl brpmoacetate (XI) to give the hydroxy-acid ester (XII) which was dehydrated by potassium acid sulphate at 90° to ethyl 3-(tetrahydro-pyranyl-4)-pentenate (XIII) and this hydrogenated to tie corresponding... 

These formulae explain the scission products of the two alkaloids and the conversion of evodiamine into rutaecarpine, and were accepted by Asahina. A partial synthesis of rutaecarpine was effected by Asahina, Irie and Ohta, who prepared the o-nitrobenzoyl derivative of 3-)3-amino-ethylindole-2-carboxylic acid, and reduced this to the corresponding amine (partial formula I), which on warming with phosphorus oxychloride in carbon tetrachloride solution furnished rutaecarpine. This synthesis was completed in 1928 by the same authors by the preparation of 3-)S-amino-ethylindole-2-carboxylic acid by the action of alcoholic potassium hydroxide on 2-keto-2 3 4 5-tetrahydro-3-carboline. An equally simple synthesis was effected almost simultaneously by Asahina, Manske and Robinson, who condensed methyl anthranilate with 2-keto-2 3 4 5-tetrahydro-3-carboline (for notation, see p. 492) by the use of phosphorus trichloride (see partial formulae II). Ohta has also synthesised rutaecarpine by heating a mixture of 2-keto-2 3 4 5-tetrahydrocarboline with isatoic anhydride at 195° for 20 minutes. 

The 17a-ethynyl compound (59) has been prepared in 88% yield from estr-4-ene-3,17-dione (58) and acetylene, at 2-3 atm pressure in tetrahydro-furan in the presence of potassium t-butoxide. Presumably the A-ring enone system is protected as the enolate anion during the course of the reaction. 

A few years later, Tatsui developed this process for use with indole bases and prepared l-methyl-l,2,3,4-tetrahydro-P-carboline 11 from tryptamine 9 and acetaldehyde 10 under acid catalysis. ... 

A -sulfinyl chiral auxiliaries have been used to prepare enantiopure tetrahydro-P-carbolines and tetrahydroisoquinolines in good yields under mild reaction conditions. Both enantiomers of V-p-toluenesulfinyltryptamine 46 could be readily prepared from the commercially available Andersen reagents.Compound 46 reacted with various aliphatic aldehydes in the presence of camphorsulfonic acid at -78 °C to give the A-sulfinyl tetrahydro-P-carbolines 47 in good yields. The major diastereomers were obtained after a single crystallization. Removal of the sulfinyl auxiliaries under mildly acidic conditions produced the tetrahydro-P-carbolines 48 as single enantiomers. 

In this connection the possibility of oxidation of these substances to the tetrahydro derivatives should be mentioned. It was made use of by Thiele and Bailey for the preparation of 6-methyl-3,5-dioxo-2,3,4,5-tetrahydro-l,2,4-triazine (6-azathymine) (46) and only recently by Grundman et al. for that of 6-azauracil (42). 

Proceeding from 5 -0-acetylazauridine (80), a mixture of 2 - and 3 -monophosphates (81, 82) was prepared by phosphorylation with polyphosphoric acid, and these were converted into the 2, 3 -cyclic phosphate (83). From the 2, 3 -0-isopropylidene derivative of 3-methyl-6-azauridine the 5 -phosphate was prepared by treatment with cyanoethylphosphate and the corresponding diphosphate from its morpholidate through the action of phosphoric acid. ° Furthermore, a diribonucleoside phosphate (85) with a natural 3 -5 internucleotide linkage was prepared from 6-azauridine, The starting material for the preparation of such derivatives was 5 -0-acetyl-2 -0 -tetrahydro-pyranyluridine-3 -phosphate (84) which was condensed with di-G-acetylazauridine (86) or with 2b3 -0-isopropylidene-6-azauridine (76) with the aid of dicyclohexylcarbodiimide. ... 

Thioxo-3-oxo-2,3,4,5-tetrahydro-l,2,4-triazine (4-thio-6-azauracil) (88) and 3,5-dithioxo-2,3,4,5-tetrahydro-l,2,4-triazine (2,4-dithio-6-azauracil) (89) w ere prepared by Hitchings et al. treating 6-aza-... 

Oxo 5-imino-2,S,J, 5-tetrahydro-l,, 4-triazine 6-Azacytosine) Substances of this type were not studied by the earlier workers, and the first representative of this group to be investigated was 3-oxo-5-imino-2,3,4,5-tetrahydro-l,2,4-triazine (122) which should bear the name 6-azacytosine. It was prepared by Falco et al. by treating 3-thioxo-5-oxo-2,3,4,5-tetrahydro-l,2,4-triazine (88) with alcoholic ammonia. Some iV-substituted derivatived were prepared anal-ogously. ... 

The preparations of over two hundred tetrahydro- and octahydro-pyrido[4,3-d]pyrimidines from piperidines or from purely aliphatic starting materials are described in the patent literature. Fully aromatic examples of the system have been prepared from pyridines and pyrimidines. 

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