Preparation of less readily

Decarboxylation of a-(4-quinazolinyl) acetic esters in alkaline solution is useful for the preparation of less readily accessible 4-alkyl quinazolines (see 4c). This method is limited to derivatives where... 

Synthetically useful procedures for the preparation of less readily available aldonic acids from bromodeoxylactones by treatment with strong bases have been demonstrated. These very simple procedures, with no or very little use of protecting groups, are attractive compared with other synthetic methods for the same compounds. 

CgHijClNjOj. Colourless, hygroscopic, m.p. 2I0-212 C (decomp.). Prepared from fi-chloroethyl carbamate and trimethylamine. It has a physiological action similar to that of acetylcholine, but more prolonged, as it is less readily hydrolysed. It is used for intestinal atony following operations, and can be given orally. 

The preparation of -butyl bromide as an example of ester formation by Method 1 (p. 95) has certain advantages over the above preparation of ethyl bromide. -Butanol is free from Excise restrictions, and the -butyl bromide is of course less volatile. and therefore more readily manipulated without loss than ethyl bromide furthermore, the n-butyl bromide boils ca. 40° below -butyl ether, and traces of the latter formed in the reaction can therefore be readily eliminated by fractional distillation. 

We will not discuss the preparation of cumulated dienes They are prepared less readily than isolated or conjugated dienes and require special methods... 

RSSiMe3 [R = Me, Et, (-CH2-)3], Zn, Et20, 0-25°, 70-95% yield. This method is satisfactory for a variety of aldehydes and ketones and is also suitable for the preparation of 1,3-dithianes. Methacrolein gives the product of Michael addition rather than the thioacetal. The less hindered of two ketones is readily protected using this methodology. ... 

High-valent ruthenium oxides (e. g., Ru04) are powerful oxidants and react readily with olefins, mostly resulting in cleavage of the double bond [132]. If reactions are performed with very short reaction times (0.5 min.) at 0 °C it is possible to control the reactivity better and thereby to obtain ds-diols. On the other hand, the use of less reactive, low-valent ruthenium complexes in combination with various terminal oxidants for the preparation of epoxides from simple olefins has been described [133]. In the more successful earlier cases, ruthenium porphyrins were used as catalysts, especially in combination with N-oxides as terminal oxidants [134, 135, 136]. Two examples are shown in Scheme 6.20, terminal olefins being oxidized in the presence of catalytic amounts of Ru-porphyrins 25 and 26 with the sterically hindered 2,6-dichloropyridine N-oxide (2,6-DCPNO) as oxidant. The use... 

The method described above may be used for the preparation of a wide variety of butenolides substituted in the arylidene ring with either electron-withdrawing or electron-releasing substituents. y-Lactones such as a-benzylidene-7-phenyl-A 1 -bu-tenolide are isoelectronic with azlactones, but have received much less attention. Like the azlactone ring, the butenolide ring may be opened readily by water, alcohols, or amines to form keto acids, keto esters, or keto amides.7 a,-Benzylidene-7-phenyl-A3,1 -butenolide is smoothly isomerized by aluminum chloride to 4-phenyl-2-naphthoic acid in 65-75% yield via intramolecular alkylation. 

The aminotin compounds are less readily prepared, and are more reactive both in substitution and addition processes, than the alkox-ides. The established routes to, and reactions of, these compounds are exemplified by recent work on the aziridine derivatives (217). 

Above 140°C its exothermic decomposition to metal and carbon dioxide readily becomes explosive [1], A 1 kg batch which had been thoroughly dried at 50°C exploded violently when mechanical grinding in an end-runner mill was attempted [2], Explosions have been experienced when drying the oxalate as low as 80°C [6], It is a compound of zero oxygen balance. The explosion temperature of the pure oxalate is lowered appreciably (from 143 to 122°C) by application of an electric field [3], The salt prepared from silver nitrate with excess of sodium oxalate is much less stable than that from excess nitrate [4], Decomposition at 125°C in glycerol prevents explosion in the preparation of silver powder [5],... 

A recent reinvestigation of this reaction has substantiated the intermediacy of the 5-coordinate methylene complex 51. Thermally unstable 51 is formed when a THF solution of 46 is treated with CH2N2 at -60°C (56). The iodo analog Ir(=CH2)I(CO)(PPh3)2 has been similarly prepared and is somewhat more stable than 51, with iodide migrating less readily to the carbene carbon than chloride (56). 

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