3-tert.-Butyl-4,5-dihydro

Compound fert-butyl 3-(2-methoxy-2-oxoethyl)-lH-indole-l-carboxylate (m-23a) [89], terf-butyl 3-formyl-5-methoxy-lff-indole-l-carboxylate [241], (3R,7aS)-3-(trichloromethyl)-tetrahydropyrrolo[l,2-c]oxazol-l(3F/)-one (III-43) [118], (3R, 7aR)-7a-allyl-3-(trichloromethyl)-tetrahydropyrrolo[ 1,2-c]oxazol-1 (3H)-one (HI-45) [121], (3R,7a5)-3-(tert-butyl)dihydro-pyrrolo[l,2-c]oxazole-l,5(3//,6//)-dione (III-46a) [125], (3R,7a5)-3-(trichloromethyl)-dihydropyrrolo[ 1,2-c]oxazole-... 

Benzopyran-3-one, l,4-dihydro-6,7-dimethoxy-], 55, 45 Isocyamde, benzyl-, 55, 98 Isocyanide, butyl-, 55, 98 ISOCYANIDE, tert-butyl- [Isocyamde, 1,1-dimethylethyl-], 55, 96 Isocyamde, cyclohexyl-, 55, 98 Isocyamde, dodecanyl-, 55, 98 Isocyamde, ethyl, 55,98 Isocyamde, methyl, 55, 98 Isocyamde, phenyl-, 55, 98 (-)-2,3 4,6-Di-0-isopropylidene-2-keto-L-gulomc acid, hydrate [L-jcy/o-2-Hex-ulosomc acid, bis-<9-( 1 -mcthylcthyl-ldene)-], 55,80, 81 ISOXAZOl F, 3-(4-chlorophenv1)-5-(4-methoxyphenyl)-, 55, 39 Isoxazole,5 -(4-chloropheny l)-3-(4-me th-oxyphenyl)-, 55,42... 

Brom-propyl)-9,10-dihydro- 673 9-tert.-Butyl-9,10-dihydro- 672 9-(2-Chlor-athyl)-9,10-dihydro- 673... 

Bromo-A -ferf-butyl-6-(2-chloroacetamido)aniline (25) gave 5-bromo-4-tert-butyl-3,4-dihydro-2(l//)-quinoxalinone (26) (EtPrjN, Nal, MeCN, reflux, 22 h 79%). ... 

Ethoxypyrrolin-5-one l-Pyrrolin-5-one, 2-ethoxy- (8) 2H-Pyrrol-2-one, 5-ethoxy-3,4-dihydro- (9) (29473-56-1) tert-Butyl N-(l-ethoxycyclopropyl)carbamate Cyclopropanecar-bamic acid, 1-ethoxy-, tert-butyl ester (8) Carbamic acid, (1-ethoxycyclopropyl)-, 1,1-dimethylethyl ester (9) (28750-48-3 41879-49-6)... 

Two types of addition to pyrimidine bases appear to exist. The first, the formation of pyrimidine photohydrates, has been the subject of a detailed review.251 Results suggest that two reactive species may be involved in the photohydration of 1,3-dimethyluracil.252 A recent example of this type of addition is to be found in 6-azacytosine (308) which forms a photohydration product (309) analogous to that found in cytosine.253 The second type of addition proceeds via radical intermediates and is illustrated by the addition of propan-2-ol to the trimethylcytosine 310 to give the alcohol 311 and the dihydro derivative 312.254 The same adduct is formed by a di-tert-butyl peroxide-initiated free radical reaction. Numerous other photoreactions involving the formation by hydrogen abstraction of hydroxyalkyl radicals and their subsequent addition to heterocycles have been reported. Systems studied include 3-aminopyrido[4,3-c]us-triazine,255 02,2 -anhydrouri-dine,256 and sym-triazolo[4,3-fe]pyridazine.257 The photoaddition of alcohols to purines is also a well-documented transformation. The stereospecific addition of methanol to the purine 313, for example, is an important step in the synthesis of coformycin.258 These reactions are frequently more... 

As reported by Padwa and coworkers, exposing a suitable nitrofuran precursor to microwave irradiation in l-methyl-2-pyrrolidone (NMP) in the presence of 2,6-luti-dine catalyst provided l,4-dihydro-2H-benzo[4,5]furo[2,3-c]pyridin-3-one as the major product in 36% yield (Scheme 6.236) [419]. In contrast, under thermal conditions, removal of the tert-butyl group was observed as the major reaction pathway. 

The reactive triflate 323 prepared from the aldol adduct 322 promoted an intramolecular attack by the BOC carbonyl group (expecting subsequent loss of a tert-butyl cation) to afford the dihydro derivative 325 through the oxonium 324 (Scheme 45) <2003OBC3749>. 

Scheme 6.76 Generation of l-oxa-2,3-cyclohexadiene (351) from 5-bromo-3,4-dihydro-2H-pyran (376) and trapping products of351 obtained from furan, 2,3-dimethyl-1,3-butadiene, 1,1-diphenyl-ethylene, ( )-l-phenylpropene, ( )-2-butene, (Z)-2-butene and tert-butyl alcohol , according to Schlosserand co-workers.

When the reaction of enaminone (223) and dimethyl methoxymethy-lenemalonate was carried out in THF in the presence of butyllithium, pyrrolidinomethylenemalonate (224) was obtained in 4% yield. When this reaction conducted in DMF in the presence of potassium tert-butylate, pyrrolidinomethylenemalonate (224) and 2,3-dihydro- l//-indolizin-5-one (225) were prepared in 21 and 46% yields, respectively (88AP345). 

Synthesis of Enantiomerically Pure p-Amino Acid from 2-tert-Butyl-1-carbomethoxy-2,3-dihydro-4(1 H)-pyrimidinone (S)-p-Tyrosine-O-methyl Ether. 

Treatment of 7-chloroamine 363 with potassium /i t/-butoxide in refluxing THE gave rise to a mixture of (Z-tert-butyl)-5,5-dimethyl-5,6-dihydro-4f/-l,3-oxazine 366 and 1-pivaloylazetidine 367 (Scheme 67). The heterocycles 366 and 367 were formed through generation of the Favorskii intermediate 364 by dehydrocyanation, which was followed by opening of the cyclopropylideneamine by /r-rt-butoxide with the subsequent loss of isobutene and a subsequent intramolecular N-alkylation or O-alkylation of the amide anion 365 <1999EJ0239>. 

The second problem results from the fact that the azaenolates exist as aggregates or mixed aggregates in ethereal solvents. Cryoscopic measurements established that the azaenolate generated from 4,5-dihydro-4-methoxymethyl-2-methyl-5-phenyloxazole and butyllithium in tetrahydrofuran is a dimer18. When the metalation was performed with butyllithium or tert-butyl-lithium, an aging effect was observed. Thus, the enantiomeric excess on alkylation drops from 43% to 28% and 11 % when the azaenolates generated at — 78 °C were allowed to warm to... 

Einen Spezialfall diirfte die photochemische Abspaltung der 4-standigen tert.-Butyl-Gruppe als Isobutan aus 4-tert.-Butyl-4,5-dihydro-l,2,4-oxadiazol zum Hetaren darstellen293, wie auch die Spaltung des kondensierten 4,5-Dihydro-l,2,4-oxadiazols I unter sauren Bedingungen326 ... 

A proton is also transferred easily to C-5. Thus by the action of methanol on 1 -lithio-2-tcr/-butyl-1,2-dihydropyridine at -70°C, a mixture of 2-tert-butylpyridine and 2-/ert-butyl-1,2,5,6-tetrahydropyridine was formed through the intermediacy of 2-tert-butyl- 1,2-dihydro- and 2-tert-butyl-2,5-dihydropyridines.137 The latter types of intermediates have been actually isolated in a number of instances to provide some general validity to the sequence shown in Eq. (17).143... 

Dihydro-2H-pyran 2H-Pyran, 3,4-dihydro- (8,9) (110-87-2) tert-Butyllithium Lithium, tert-butyl- (8) Lithium, (1,1-dimethylethyl)- (9) (594-19-4) Palladium(ll) chloride bisacetonitrile Aldrich Bis(acetonitrile)dichloropalladium(ll) Palladium, bis(acetonitrile)dichloro- (8,9) (14592-56-4)... 

The difference in conformational free energy of the N-Me group in N-methylpiperidine (2.7 kcal mol-1, favoring N-Meeq) and in N-methyltetra-hydro-l,3-thiazine (0.7 kcal mol-1, favoring lV-Meax at -120°C) suggests the predominance of the lV-Meax conformer 463 of 5-methyldihydro-1,3,5-dithiazine (462 R = Me). Indeed, H-NMR spectra and dipole-moment data show that NR axial is the predominant conformer for a series of AT-alkyl-dihydro-l,3,5-dithiazines (462 R = Me, Et, iPr, -Bu).356 This even applies to the Af-tert-butyl compound, which possesses an unconstrained axial tert-butyl group.357... 

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