Yields were particularly good (69–79%) when aryltrimethylstannanes were treated with caesium fluoroxysulfate (Equation (32)) <86BSF930, 86CC1623>. Arylmercury compounds have been fluorinated with acetyl hypofluorite (Equation (33)) <84CC655, 86JOC1886, 88TL1501>. Monitoring of the reaction by NMR showed that the compound 249 predominates in the reaction mixture after 30 min. Its reactions with a range of haloarenes, including designed 2,6-dialkylhaloarenes, were studied in THF and in benzene. The transformations of the epimeric vinylcyclobutanols (175) and (178), studied by both Danheiser64 and Cohen,65 are representative (Scheme 19). "(−)-α-Pinene by Isomerization of (−)-β-Pinene", Hydrogen chalcogenides (Group 16 hydrides), https://en.wikipedia.org/w/index.php?title=Potassium_hydride&oldid=979056432, Chemical articles with multiple compound IDs, Multiple chemicals in an infobox that need indexing, Pages using collapsible list with both background and text-align in titlestyle, Articles containing unverified chemical infoboxes, Creative Commons Attribution-ShareAlike License, This page was last edited on 18 September 2020, at 14:27. Likewise, alkylation of the silver salts of (74) affords mixtures of O- and N-alkyl products 〈64HCA838〉 while the sodium salt furnishes the thermodynamically preferred N-alkyl compound with ethyl chloroacetate 〈84CB2999〉. Further studies defining the scope and stereochemical course of the oxyanion-accelerated vinylcyclobutane rearrangement were subsequently carried out in the laboratories of Danheiser64 and Cohen.65 Potassium, sodium66 and even lithium alkoxides have been employed as the activating substituent in these reactions. In summary then, the oxyanion-accelerated rearrangement of 2-vinylcyclobutanol derivatives is now established as an attractive method for achieving two-carbon ring expansion under relatively mild conditions. KC5H5 above).68 There are weaker η2 interactions between the potassium ions of one chain and the C5H5 rings attached to the adjacent chain (K–C ca. 26), and NMR data suggest that the monomeric structure is retained in pyridine solution. Weise, in Comprehensive Organic Synthesis II (Second Edition), 2014. Potassium hydride and sodium hydride are flammable solids that ignite on contact with moist air. From: Studies in Natural Products Chemistry, 2016, LAWRENCE Y. Potassium reacts wiolently with water, forming potassion hydroxide, KOH, and hydrogen gas, H 2. Potassium hydride presents a more serious fire hazard than sodium hydride. Objective. Other oxadiazolones of type (79) fragment to CO2, a nitrile, a nitrene, and a carbene finally leading to a host of products 〈79JCS(P1)483〉. Formation of the phosphole complex [(C4PMe2Ph)4Na2(DME)2], 46, and the anion in the potassium compound trans-[K([18]-crown-6)(THF)2]2[K(C4PMe2Ph)2THF]2. However, preparation of 4-chlorocarbonyl compounds (73) can be achieved by cycloaddition of stable nitrile oxides to the CN double bond of chlorocarbonyl isocyanate 〈88S994, 90ZOR339〉. C. Schneider, C.F. Balancing chemical equations. 1H NMR (CDCl3, δ ppm) 2.43 (s, 3H), 7.26 (d, 2 H, J = 8), 7.81 (d, 2 H, J = 8); mass spectrum, m/z (rel. Acetylation of compound (71) with acetic anhydride in pyridine produces the N(2)-acetylated compound (72) (x-ray analyzes) (Equation (16)). Sodium hydride and potassium hydride fires must be extinguished with a class D dry chemical extinguisher or by the use of sand, … [6] Evaporation of the solvent left a light yellow oil, to which was added 30 mL abs EtOH and 2.27 g (9.32 mmol) p-toluenesulfonylhydrazide. 4,5-Dihydro-1,2,4-oxadiazol-5-ones (74) cannot be N-acylated by either chlorocarbonyl isocyanate or trichloroacetyl chloride. The compounds M[(C5HMe4)2Ti(η1-C=CSiMe3)2] (M = Na, K, Rb, Cs) were made from reactions between the metals and the compound with M = Li. However, it was found that VCB rearrangement can be achieved in this and other difficult cases by means of the corresponding potassium salts, which are conveniently generated in situ from 2-vinylcyclobutanones under the conditions described in equation (28). The reaction of α,α-dihalogeno bicyclo[3.3.1]nonanediones 262 under Favorskii raction conditions in the presence of sodium methoxide, ethoxide, propoxide, and potassium cyanide led to the intramolecular ring closure via C–O bond formation giving the highly functionalized chiral 2-oxatricyclo[4.3.1.03,8]decanes (2-oxaprotoadamantane) 264. Decomposes when heated, pressurized H2 melts without decomposition. In the potassium compound 41 (Fig. Although 134 required heating under reflux in THF for over 22 h to give rise to 135, the additional unsaturation in 136 greatly facilitated the process and led to a quantitative rearrangement to furnish 137 within just 2 h at room temperature.53, E. Butkus, in Comprehensive Organic Synthesis II (Second Edition), 2014, Treatment of 3,3,8-tribromocamphor 248 with potassium anilide (generated in situ from potassium hydride and aniline) in THF at room temperature for 7 h lead to an interesting tricyclic compound 250 in 85%. The subsequent intramolecular nucleophilic attack of the bromine atom by the anionic oxygen led to the cyclic ether formation. Arylstannanes have been fluorinated with fluorine, fluoroxytrifluoromethane and caesium fluoroxysulfate. The compound NaC5HPh4.DME, 45, obtained from C5H2Ph4 and a sodium mirror in DME, has a structure (Fig. The process leading to the intramolecular ring closure can be explained by a pathway implying intermediate alkoxy bicyclo[3.3.1]nonanolate species 263 (Scheme 83).107 The anion 263 is the key intermediate in the process and halogen is released during an intramolecular process at C-7 and not at C-3 as in a usual Favorskii process. The related compound KC5H4CH2CHMe2 has been made from potassium hydride and isobutylcyclopentadiene. Christopher J. Urch, in Comprehensive Organic Functional Group Transformations, 1995. Methylation of oxadiazoles (74) with diazomethane gives mixtures of O- and N-methyl products (Scheme 27) 〈65T1681, 81JCS(P1)1703〉. 2 K (s) + 2 H 2 O (l) 2 KOH (aq) + H 2 (g) Quantitative analysis. Storage and Handling: Sodium hydride and potassium hydride should be handled in the laboratory using the "basic prudent practices" described in Chapter 5.C, supplemented by the additional precautions for work with flammable (Chapter 5.F) and highly reactive (Chapter 5.G) substances. The oxyanion-accelerated VCB rearrangement proceeded smoothly in this case at only 0 C, and produced the tetracyclic steroid model compound (204) in 90% yield. (b) Use data in Figures 7.10 and 7.12 to determine the energy change in kJ/mol for the following two reactions: For instance, 1-napthol with potassium hydride gave 2-fluoro-1-napthol in 60% yield and phenyl-magnesium bromide gave fluorobenzene in 50% yield. KH reacts with water according to the reaction: KH + H 2 O → KOH + H 2. Intramolecular nucleophilic ring opening at C-6 followed by protonation provides 256, whereas nucleophilic attack at C-8 followed by an intramolecular aldol-addition to the keto group leads to the tetracyclic ketol 257 (Scheme 81).106, The dehydrobromination of similar dibromo ester 259 with either DBU in THF or with LiBr/Li2CO3 in DMF gave tetracyclic 261 as the sole product in 70% isolated yield.