Carbonyl compounds imidazole

Azirine, trans-2-methyl-3-phenyl-racemization, 7, 33, 34 1-Azirine, 2-phenyl-reactions, 7, 69 with carbon disulfide, S, 153 1-Azirine, 3-vinyl-rearrangements, 7, 67 Azirines, 7, 47-93 cycloaddition reactions, 7, 26 fused ring derivatives, 7, 47-93 imidazole synthesis from, 5, 487-488 photochemical addition reactions to carbonyl compounds, 7, 56 photolysis, 5, 780, 7, 28 protonated... 

The carbonylation of imidazole derivatives with several olefins takes place in high yields with the aid of an Ru3(CO)i2 catalyst.112,112a The carbonylation occurs exclusively at the a-position to the sp2 nitrogen (Equation (85)). A wide range of olefins can be utilized in this reaction, and a variety of functional groups are compatible under the reaction conditions. The (/i-H)triruthenium clusters such as 12 are proposed as a key species in this carbonylation reaction. Other five-membered A-heteroaromatic compounds, such as pyrazoles, oxazoles, and thiazoles, can be used for the carbonylation reactions, where the carbonylation takes place at the a-C-H bond to the sp2 nitrogen. 

This benzilic acid type of rearrangement is the result of the action of alkali on the dicarbonyl compound, and is accelerated by calcium ions. The formation of saccharinic acids by the action of aqueous alkali on sugars is very well known 82,84,92 however, if ammonia is present, very little8 or no production of saccharinic acid has been reported. The reaction of the intermediate carbonyl compounds with ammonia is faster than the benzilic acid type of rearrangement to give saccharinic acid, and, hence, substituted imidazoles are formed, as illustrated in Scheme 9. 

Diethyl [(2-tetrahydropyranyloxy)methyl]phosphonate is useful in the Wlttig-Horner synthesis of enol ethers, which are intermediates in one-carbon homologations of carbonyl compounds. This procedure is an adaptation of a general method for making dialkyl hydroxymethylphosphonates. An 0-tetra-hydropyranyl derivative also has been made from dibutyl hydroxymethyl -phosphonate, and diethyl hydroxymethylphosphonate has been O-silylated with tert-butylchiorodimethylsilane and imidazole. Another useful congener in this series has been prepared by an Arbuzov reaction of methoxyethoxymethyl (HEM) chloride and triethyl phosphite. 

An interesting example of heterocyclization involving both the aziridine fragment and the carbonyl group is a reaction of aziridinyl ketones with ammonia and carbonyl compounds, giving rise to 3,5a-dihydro-l//-azireno[l,2-c]imidazoles. This reaction will be considered in more detail in Sects. 1.2 and 1.3. 

One of the initial findings about bicyclic aziridines is reported in [88] the authors carried out the synthesis of 3,5a-dihydro-l//-azireno[l,2-c]imidazoles by reacting trwith carbonyl compounds in methanol saturated with ammonia in the presence of ammonium bromide. In particular, 2,2-dimethyl-6-(4-nitrophenyl)-4-phenyl-l,3-diazabicyclo[3.1.0]hex-3-ene 72 was obtained in the reaction of ketone 70 with ammonia and acetone 71 (Scheme 1.19). 

Alcohols containing nitrogen heterocycles are also smoothly oxidized to the corresponding carbonyl compounds. These heterocycles include pyridine, imidazole and triazole derivatives. 

Carbonyl compounds and other dipolarophiles containing heteroatoms react with miinch-nones. Thus benzaldehyde forms the betaine (245) which suffers ring-cleavage to yield the enamine (246 equation 65). Thiocarbonyl compounds and nitrosobenzene behave in an analogous manner. The action of dipolarophiles containing cumulative double bonds results in the formation of new mesoionic systems. Thus carbon disulfide and phenyl isothiocyanate afford a zwitterionic thiazole and imidazole, respectively (Scheme 25). 

For some indoles it is necessary to control regioselectivity with nnsymmetrical carbonyl compounds. Ondansetron, the anti-nausea compound that is used to help cancer patients take larger doses of antitumour compounds than was previously possible, is an example. It contains an indole and an imidazole ring. 

The cyclic a-lithio-l,3-dithiane S-oxide 406 was generated from compound 392 with n-BuLi at —10 °C and reacted with deuterium oxide, alkyl halides, carbonyl compounds and esters to afford the corresponding products 407 as mixture of diastereomers (Scheme 106)605 - 607. (V-Acyl imidazoles were better acylating agents than esters608. However, compound 406 has not been employed properly as acyl anion. Intermediate... 

Reactions of 3-hydrazino-l,2,4-triazin-5-one derivatives with carbonyl compounds to give triazolotriazine derivatives have been reported <03KGS1376>. Intramolecular inverse electron demand cycloadditions of 2-substituted imidazoles with various 1,2,4-triazines produced both imidazo[4,5-c]pyridines (3-deazapurines) and pyrido[3,2-[Pg.387]

The treatment of vinyl anions with elemental selenium also leads to seleno-carbonyl compounds via eneselenolate anions (Eqs. 4-6). Deprotonation of l,3-selenothio-2-thione with EDA followed by the reaction with elemental selenium proceeds accompanied with the rearrangement of vinylic skeleton to form l,3-dithio-2-selone derivatives (Eq. 4) [38]. The vinyl anions from oxa-zolines and imidazoles were treated with elemental selenium to give the oxazo-line selone and imidazoline selone after the aqueous workup (Eq. 5) [39]. The reaction of vinyl magnesium halides with elemental selenium and allyl bromide gives allyl vinyl selenides that undergo a seleno-Claisen rearrangement to generate y,6-unsaturated selenoaldehydes (Eq. 6) [40]. 

Rather less common are condensations between a-hydroxyketones, ammonia and an imidate. Equivalent amounts of the hydrochloride salt of the imidate and the or-substituted carbonyl compound (cr-halogeno-and a-acetoxyketones also take part) are heated (40-70°C) in liquid ammonia (3-48 h) at elevated pressures. Yields of imidazoles vary between 10 and 90%, but the requirements of working with liquid anomonia in an autoclave may make this approach unappealing if alternatives are available [42,43]. Examples include 4-hydroxymethyl- (35%), 4-hydroxymethyl-2-phenyl- (73%), 4-hydroxymethyl-2-(p-tolyl)- (68%) and 2-benzyl-4-hydroxymethylimidazoles (85%) [44]. 

Cyclization of l-aroyl-3-arylthioureas 1355 with a variety of carbonyl compounds bearing an a-H, in the presence of bromine and triethylamine, provides 1-aroyl-3-aryW-substituted imidazole-2-thiones 1356 <20030L1657>. The underlying mechanism of this condensation is illustrated in Scheme 348. 

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