3- methylene-2,3-dihydro

The palladium-catalyzed cyclocarbonylation reaction of o-iodoanilines with allenes and CO in l-butyl-3-methylimidazolium hexafluorophosphate [bmimJPFg afforded 3-methylene-2,3-dihydro-lH-quinolin-4-ones in yields of up to 90% under a low pressure (5 atm) of CO (Scheme 17.2). The ionic liquid, as the solvent and promoter, enhanced the efficiency of the cyclocarbonylation reaction. In this work. Ye and group demonstrated the recyclability of the system of ionic liquids and their use as catalysts [44]. 

Carbonylation of 2-iodophenol (91) in the presence of 1,2-nonadiene (95) afforded 2-(n-hexyl)-3-methylene-2,3-dihydro-4/f-l-benzopyran -one (97) in 74% yield, showing that selective attack of phenoxy group at the substituted terminus of r-allylpalladium intermediate 96 occurred. Uses of DPPB and K2CO3 were important [43]. 

Benzyl-3-hydroxy-3-methyl-2,3-dihydro-lH-pyrrolo[3,4-c]quinolin-l-one refluxed 3 hrs. in acetic anhydride -> 2-benzyl-3-methylene-2,3-dihydro-lH-pyrrolo[3,4-c]-quinolin-l-one. Y 90%. H. Fritz and S. Schenk, A. 1975, 255. 

A Pd(PhCN)2Cl2-catalyzed cyclization of 3-propargylthio-1,2,4-triazines affording a mixture of 6-methylene-6,7-dihydro-4//-thiazolo[2,3-c][l,2,4]triazin-4-ones and 3-methylene-2,3-dihydro-7//-thiazolo[3,2-b][l,2,4]triazin-7-ones has also been reported (eq 72). ... 

In den Fallen 30f—30g — sinngemaC bei den Methylen-dihydro-pleiadenen 31 a und 31b — bedeutet der Vorgang A B die Umwandlung von Enantiomeren ineinander. 

Ch cholesterol. Erg Ergosterol, Obt Obtusifoliol 24-M 24 - methylene dihydro lanosterol. 

The H C ratio in hydrocarbons is indicative of the hydrogen deficiency of the system. As mentioned, the highest theoretical H C ratio possible for hydrocarbon is 4 (in CH4), although in electron-deficient carbocationic compounds such as CH5 and even CH/, the ratio is further increased (to 5 and 6, respectively, see Chapter 10). On the other end of the scale in extreme cases, such as the dihydro- or methylene derivatives of recently discovered Cgo and C70 fullerenes, the H C ratio can be as low as 0.03. 

Reactions. Heating an aqueous solution of malonic acid above 70°C results in its decomposition to acetic acid and carbon dioxide. Malonic acid is a useful tool for synthesizing a-unsaturated carboxyUc acids because of its abiUty to undergo decarboxylation and condensation with aldehydes or ketones at the methylene group. Cinnamic acids are formed from the reaction of malonic acid and benzaldehyde derivatives (1). If aUphatic aldehydes are used acryhc acids result (2). Similarly this facile decarboxylation combined with the condensation with an activated double bond yields a-substituted acetic acid derivatives. For example, 4-thiazohdine acetic acids (2) are readily prepared from 2,5-dihydro-l,3-thiazoles (3). A further feature of malonic acid is that it does not form an anhydride when heated with phosphorous pentoxide [1314-56-3] but rather carbon suboxide [504-64-3] [0=C=C=0], a toxic gas that reacts with water to reform malonic acid. 

Tc(III)(l, 2-bis((dihydro-2,2, 5,5-tetramethyl3(2i/)-furanonato)methylene)amino)ethane)(TMPP)2 ( Tc-furifosrnin), where... 

Active methylene compounds can add to 1,3-dithiolylium ions to give 2-substituted 1,2-dihydro-1,3-dithioles (206). Again, addition is often followed by oxidation (to 207). Alternatively, further addition can occur (to 208) (80AHC(27)151). In this reaction, (205) can be CH2(CN)2, CH2(COMe)2 or even MeCOMe. Somewhat similar reactions are shown by 1,3-diarylimidazolium ions. 

H-Azepine, 2-(o-hydroxyphenyl)-synthesis, 7, 538 3 H-Azepine, methyl- H NMR, 7, 495 3H-Azepine, 3-methylring inversion barrier, 7, 14 3 H-Azepine, 2-methylene-isomerization, 7, 505 3H-Azepine, 7-(N-phthalimido) synthesis, 7, 538 4H-Azepine, 4,5-dihydro-cyclization, 7, 524... 

Furan, 2,3-dihydro-5-methyl-polymers, 1, 276 Furan, 2,3-dihydro-3-methylene- H NMR, 4, 577 Furan, 2,5-dihydro-2-methylene- H NMR, 4, 577 tautomerism aromaticity and, 4, 595 Furan, 2,5-dihydro-2-nitro-structure, 4, 550 Furan, 2,3-dihydroxy-tautomerism, 4, 37 Furan, 2,4-dihydroxy-tautomerism, 4, 37 Furan, 3,4-dihydroxy-tautomerism, 4, 37 Furan, 2,5-diiodo-nitration, 4, 602 synthesis, 4, 712 Furan, 3,4-diiodo-reactions, 4, 650 Furan, 2,3-dimethoxy-synthesis, 4, 625, 648 Furan, 2,5-dimethoxy-synthesis, 4, 648 Furan, 3,4-dimethoxy-cycloaddition reactions, 4, 64, 625 lithiation, 4, 651 reactions... 

H-l,2-Oxazine-3-carboxylic acid, 5,6-dihydro-synthesis, 1, 484 Oxazine-4,6-dione, 2-methylene-synthesis, 3, 1031... 

Oxazole, 2,5-dihydro-4-methoxy-synthesis, 6, 228 Oxazole, dihydro-2-methylene-reactions, 6, 215... 

Pteridine, 2-amino-4-methoxy-6,8-dimethyl-7-methylene-7,8-dihydro-... 

Selenophene, 2,5-diamino-3,4-dicyano-synthesis, 4, 119, 964 Selenophene, 2,4-diaryl-synthesis, 4, 967 UV spectra, 4, 941 Selenophene, 2,5-diaryl-synthesis, 4, 967, 969 UV spectra, 4, 941 Selenophene, 2,5-dichloro-metallation, 4, 949 Selenophene, dihydro-3-methylene-synthesis, 4, 963 Selenophene, 2,5-dimethoxy-lithiation, 4, 949 Selenophene, 2,4-dimethyl-... 

The next seven references are cited not because of the experimental procedures described but because they indicate diversification in the types of enamines prepared and studied. Both Paquette (25) and Kasper 26) have condensed 2,5-methylene-l,2,5,6-tetrahydrobenzaldehyde (5-nor-bornene-2-carboxyaldehyde) (2) with several cyclic and open-chain aliphatic secondary amines. Kasper studied the ratio of endo to exo aldehyde formed upon hydrolysis of these enamines and the dihydro enamines. Paquette investigated the addition of sulfene to the enamines. -Fluoro-... 

Other examples of CN/CC replacement are observed in reactions of l-phenyl-pyrimidin-2(l//)-one with active methylene compounds, such as diethyl malonate and benzoylacetate, giving in good yield 2-oxo-l,2-dihydro-3-pyridinecarboxylate and 3-benzoylpyridin-2(l H)-one, respectively (84CPB2942, 87H2223) (Scheme 8). In a similar way 4,6-dimethyl-1-phenylpyrimidin-2( 1 //)-one, 4,6-dimethyl-1 -phenylpyrimidine-2( 1 //)-thione and 4,6-dimethyl-1 -phenyl-2-phenylimino-1,2-dihydropyrimidine yield with malonitrile 2-amino-4,6-dimethyl-3-pyridinecarbonitrile. In a similar way 2,3-diarylpyrimidin-4(3//)-thiones give with malonitrile CN/CC replacement (84H763) (Scheme 8). The reaction takes a similar course as described in Scheme 7. 

D) Preparation of 2-(1-Hydroxyethyi)-3-Methyi-5-(2-Oxo-2,5-Dihydro-4-Furyi)Benzo[b] Furan (3574 CB) 13,2 grams of compound 3556 CB of which the preparation is described in (C) are treated successively with 66 ml of methylene chloride, 27 ml of methanol and, with stirring, 1.6 grams of sodium borohydride added in stages. The reaciton takes 1 hour. The mixture is poured into water acidified with a sufficient amount of acetic acid, the solvents are stripped under vacuum, the crystalline product removed, washed with water, and recrystallized from ethyl acetate. Yield 90%. MP <=158°C. 

Chemical Name 8-Nitro-1,2-dihydro-2-(N-methyl-piperazin-1 -yl)methylene-6-(o-chloro-phenyl)-1 H,4H-imidazo-[ 1,2-a] [ 1,4] -benzodiazepin-1 -one methanesulfonate... 

Step 2 5-(p-Chlorophenyll-5-Hydroxy-2,3-Dihydro-5H-lmidazo[2,1 -a]Isoindole 1-(p-Chlorophenyl)-3-ethoxy-1 H-isoindole (1 g), 2 g of ethyleneimine hydrotetrafluoroborate moistened with methylene chloride (containing approximately 0.66 g of dry salt) is refluxed in 25 ml of absolute toluene for 2 hours in an atmosphere of nitrogen. The result-... 

A mixture of 26 parts of 3-carbethoxy-6,7-methylenedioxy-4-hydroxy-quinoline, 16 parts of sodium hydroxide and 50 parts of dimethylformamide is heated at 70° to 75°C for 2 hours, then 31 parts of ethyl iodide is added over 1 hour with continued heating and stirring. After an additional 3 to 4 hours of heating (at 70° to 75°C) and stirring, the mixture is diluted with 500 parts of water, refluxed for 3 to 4 hours, acidified with concentrated hydrochloric acid and filtered to yield 18 to 22 parts of 1-ethyl-1,4-dihydro-6,7-methylene-dioxy-4-oxo-3-quinoline-carboxylic acid, MP 309° to 314°C (decomposes). The analytical sample from dimethylformamide melts at 314° to 316°C (decomposes). 

D/chloro-5-Cyclohexyl-2-Oxo-2,3-D/hydro 1 H-Benzo(fj-Diazepine-1,4 fa) Process Using Sodium Hypochlorite — 40 ml of a solution of sodium hypochlorite of 14.5 British chloro-metric degrees are added to a suspension of 5.4 grams of 7 chloro-5 cyclohexyl-2 oxo-2,3-dihydro 1 H-benzo(f)diazepine-1,4 in BO ml of methylene chloride. The mixture is stirred at room temperature for 15 minutes the solid dissolves rapidly. The organic iayer is decanted, washed with water, dried over anhydrous Sodium sulfate and the solvent evaporated under reduced pressure without exceeding a temperature of 30 C. The residue is taken up in a little diisopropyl ether and the crystals which form are dried. They are recrystallized as rapidly as possible from ethyl acetate. Colorless crystals are obtained (3.9 grams yield, B5%) MP < = 163°C, with decomposition. 

This reaction can also be used for the synthesis of substituted 1-benzoxepins with one modification instead of the 4/T-benzopyran the 2/7-isomer must be used. 2-[Diazo(phosphoryl)meth-yl]-2//-benzopyrans decompose in the presence of ))3-allylpalladium chloride dimer with elimination of nitrogen to give 1-benzoxepins 2.192 In some cases, the reaction takes a different course and gives 2-methylene-2//-benzopyrans 3.192 In this respect, the bicyclic system behaves differently to the monocyclic diazo(pyranyl)methane. The 2-isomers of the latter structure could not be isolated and gave l//-l,2-diazepines.190 The 4//-benzopyrans do not form benzoxepins but undergo an intramolecular [2+1] cycloaddition to 3,4-dihydro-2,3,4-metheno-2//-ben-... 

Curiously, 6-(chloromethyl)-4-methyl-2-methylene-3-phenyl-3-azabicyclo[4.1.0]hept-4-ene-l,5-dicarbonitrile (31), obtained from 4,4-bis(chloromethyl)-2,6-dimethyl-l-phenyl-1,4-dihydro-pyridine-3,5-dicarbonitrile, rearranges via 4-(chloromethyl)-7-methyl-2-methylene-l-phenyl-2, 5-dihydro-l//-azepine-3,6-dicarbonitrile (32) to yield the 4-(chloromethylene)-4,5-dihydro-1//-azepine 33 as the final product.127... 

A diatropic cation 15 is also noted in strong acid solution for 7//-pyrrolo[l,2-a]azepin-7-one (14), prepared by dehydrogenation of its 5,6-dihydro derivative 13.217 It is presumed that the deep-red solution produced on treating 7-methylene-7//-pyrrolo[l,2- azepine (16), prepared from the ketone 13 as indicated, with strong acid is indicative of the formation of 7-methylpyrrolo[l,2-a]azepinium cation 17 however, the salt could not be isolated nor a satisfactory HNMR spectrum obtained.217... 

Optically active dihydro-2-methylene-2(3//)-furanones fused to 5- and 6-membered carbocyclic rings were synthesized with 64-92% ee using the intramolecular reaction between chiral 2-alkoxy-carbonylallylsilanes and aldehydes80. 

S)-Dihydro-3-methylene-5-(2-methylpropyl)-2(3//)-furanone Typical Procedure9 ... 

S-[3-terl-buto.xycarh 61% d.r. iantijsyn) >70 30... 

Ethyl (Z)-2-bromomethyl-2-heptenoate and aldehydes condense on reaction with chromium(II) chloride to furnish cw-3,4-disubstituted dihydro-3-methylene-2(3 //)-( uranones exclusively16, indicating that a (Z)-allylchromium complex might serve as reactive intermediate in the. mv-selec-tive addition step due to the bulky 2-substitucnt. Alternatively, an acyclic transition state for the reaction of the ( )-diastereomer, mediated by the Lewis acid dichloroaluminum hydride, has been discussed16. 

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