Methyl orthoformate

Similarly, reaction of (3) with methyl orthoformate yields the trimethoxy compound (6) via the intermediate 1,4-adduct (5). 

As inert as the C-25 lactone carbonyl has been during the course of this synthesis, it can serve the role of electrophile in a reaction with a nucleophile. For example, addition of benzyloxymethyl-lithium29 to a cold (-78 °C) solution of 41 in THF, followed by treatment of the intermediate hemiketal with methyl orthoformate under acidic conditions, provides intermediate 42 in 80% overall yield. Reduction of the carbon-bromine bond in 42 with concomitant -elimination of the C-9 ether oxygen is achieved with Zn-Cu couple and sodium iodide at 60 °C in DMF. Under these reaction conditions, it is conceivable that the bromine substituent in 42 is replaced by iodine, after which event reductive elimination occurs. Silylation of the newly formed tertiary hydroxyl group at C-12 with triethylsilyl perchlorate, followed by oxidative cleavage of the olefin with ozone, results in the formation of key intermediate 3 in 85 % yield from 42. 

For the preparation of methyl orthoformate, solid sodium methoxide, methanol and chloroform were mixed together. The mixture boiled violently and then exploded [1]. The analogous preparation of ethyl orthoformate [2] involves the slow addition of sodium or sodium ethoxide solution to a chloroform-ethanol mixture. The explosion was caused by the addition of the solid sodium methoxide as one portion. See Sodium, etc., above... 

Wolfbeis investigated the reactions of amines and orthoesters with different CH-acid molecules (81CB3471). When the reactions of aniline, ethyl orthoformate, and dialkyl malonates (2 mol) were carried out at 130-140°C for 4 hr, phenylaminomethylenemalonamates (245) were obtained (81CB3471). Similar reactions with aliphatic amines were unsuccessful. Phenylaminomethylenemalonic acid could not be prepared in the reactions of aniline, methyl orthoformate or orthoacetate, and malonic acid. When these reactions were carried out in 2-propanol, only amidines (246) were obtained. 

Isopropylidene methoxymethylenemalonate (420), prepared from Mel-drum s acid (421) and methyl orthoformate, was reacted with urea and thiourea under reflux for 2 hr to give aminomethylenemalonates (439) in 82% and 72% yields, respectively (84SC961). 

Amino-3-benzyloxypyridine (X = CH)and4-amino-5-benzyloxypyri-midine (X = N) were reacted with Meldrum s acid (421) and methyl orthoformate in the presence of zinc chloride to give (hetarylamino)methylene-malonates (447) (89TL1529). 

The hemiacetal hydroxyl group of the aldopyranosuloses 325 was usually protected in the form of the methyl glycoside by treatment with methyl orthoformate in the presence of a Lewis-acid catalyst.208 Higher yields of the corresponding methyl glycosides could be obtained by treatment of a glycopyranosulose with methyl iodide in the presence of silver oxide.211 One-step transformation of the dihydro-furan derivatives 324 into the methyl glycosides (326, 327) by treatment with methanol and formic or trifluoroacetic acid has been reported.212... 

Using (+)-(S)-2-butanol having [a] 5 +8.402° (optical purity 61.64%) and letting it react with methyl orthoformate affords a 67 % yield of 2-butyl orthoformate having [a]g +28.40° (61.58% optical purity) [38]. 

A mixture consisting of 100 gm (1.85 moles) of powdered sodium methoxide suspended in 120 gm of benzene (or crude methyl orthoformate) is heated to 50°C and then 74 gm (0.62 mole) of chloroform is added dropwise over a 1 hr period, the reaction temperature being kept between 60°-80°C. The precipitated sodium chloride is removed by filtration and the filtrate distilled to afford 552 gm (84%), b.p. 103°-105°C, ng 1.3770. 

Insertion reactions of methylene with methyl orthoformate or 2-methoxy-1,3-dioxolane in the gas phase and in solution [211]. 

Methyl-2-nitrosopropane dimer, 413 1 -Methyl-A8-octahydroquinoline, 111-112 yV-Methyl-A -octahydroquinoline, 111-112 Methyl orthoformate, 47, 54 Methyl orthovalerate, 48 2-Methyl-4-oximino-3-pentanone, 396 1 -(N-Methyl-7V-phenylamino)-2-bromo-propane, 105... 

SYNS METHYLESTER KYSEUNY ORTHOMRAVENCI (CZECH) METHYL ORTHOFORMATE ORTHO-FORMIC ACID, TRIMETHYL ESTER ORTHOMRAVEN-CAN METHYLNATY (CZECH) TRIMETHO-XYMETHANE... 

METHYL-ONN-AZOXY)METHYDp-d-GLUCOPYRANOSIDE see COUOOO METHYL ORTHOFORMATE see TLX600 METHYL ORTHOSIUCATE see MPI750 METFIYL ORTHOSILICATE (DOT) see MPI750 9-METHYL-3-OXA-9-... 

Preparation of Dimer. Hexamethoxydisiloxane [(CH30)3Si]20, termed dimer in this chapter, was synthesized by the method of Klemperer et al. (10) with modifications. By using Schlenk techniques, hexachlorodisiloxane (57 mL, 0.312 mol) was added dropwise (over 50 min) to a solution of freshly distilled methyl orthoformate (trimethoxymethane) (400 mL, 3.74 mol) in heptane (200 mL, dried over Na). The reaction was carried out under argon, and the temperature of the reaction mixture was maintained at 50 °C for 5 h. The mixture was stored overnight at room temperature under argon. Purification by vacuum distillation was carried out. The fraction boiling at 50 °C (43-53 Pa) was collected. Final purification to remove HCl was... 

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