Ketones reactions with diazoalkanes

Catalytic cyclopropanation of alkenes has been reported by the use of diazoalkanes and electron-rich olefins in the presence of catalytic amounts of pentacarbonyl(rj2-ris-cyclooctene)chromium [23a,b] (Scheme 6) and by treatment of conjugated ene-yne ketone derivatives with different alkyl- and donor-substituted alkenes in the presence of a catalytic amount of pentacarbon-ylchromium tetrahydrofuran complex [23c]. These [2S+1C] cycloaddition reactions catalysed by a Cr(0) complex proceed at room temperature and involve the formation of a non-heteroatom-stabilised carbene complex as intermediate. 

The reaction of ketones with diazoalkanes sometimes leads to a ring-expanded ketone in synthetically useful yields.32 The reaction occurs by addition of the diazoalkane, followed by elimination of nitrogen and migration ... 

The O-alkylation of carboxylates is a useful alternative to the acid-catalyzed esterification of carboxylic acids with alcohols. Carboxylates are weak, hard nucleophiles which are alkylated quickly by carbocations and by highly reactive, carbocation-like electrophiles (e.g. trityl or some benzhydryl halides). Suitable procedures include treatment of carboxylic acids with alcohols under the conditions of the Mitsunobu reaction [122], or with diazoalkanes. With soft electrophiles, such as alkyl iodides, alkylation of carboxylic acid salts proceeds more slowly, but in polar aprotic solvents, such as DMF, or with non-coordinating cations acceptable rates can still be achieved. Alkylating agents with a high tendency to O-alkylate carboxylates include a-halo ketones [42], dimethyl sulfate [100,123], and benzyl halides (Scheme 6.31). 

Two types of products are generally obtained by reaction of ketones with diazoalkanes a homologous carbonyl compound and a small amount of oxirane. The reaction scheme is presented in Eq. 85. 

Addition of the diazoalkane nucleophile is followed by an reaction with ring-closure or a homologous ketone is formed with a 1,2-alkyl rearrangement (shift). Spirooxiranes are produced from cyclic ketone derivatives with diazomethane (Eq. 86). ... 

A significant advance in the study of cyclopropanones resulted from studies by the Turro and the de Boer groups on the formation of cyclopropanones in solution by the reaction of ketenes with diazoalkanes. These investigators found that it is possible to store the parent ketone only for short periods at low temperature because of its unusual reactivity and propensity for polymerization. Subsequent work has shown that cyclopropanone seems to show chemical behavior similar to that of ketene. Thus, it is attacked by nucleophilic species such as water, alcohol and amines and reacts rapidly with itself to form... 

The high nucleophilicity of a-selenoalkyllithiums towards carbonyl conqiounds, even those that are the most hindered or enolizable, such as 2,2,6-trimethyl- and 2,2,6,6-tetramethyl-cyclohexanone (Schemes 113 and 164), di-t-butyl ketone, pennethylcyclobutanone, peimethylcyclopenta-none (Schemes 113 and 187) °- and deoxybenzoin (Schemes 115, 116 and i65y 4 49 23 iqws the synthesis of related alkenes, epoxides and rearranged ketones which are not available from the same carbonyl compounds on reaction with phosphorus or sulfur ylides - or diazoalkanes. ... 

In the rearrangement reaction, the multistep sequence offers the definite advantage of avoiding the polyhomologation of cyclic ketones, often encountered with diazoalkanes due to the presence of the reagent with both the starting and reananged ketone. 

Three-membered heterocycles. Decomposition of diazo compounds by the iron complex in the presence of imines leads to aziridines. An analogous reaction of diazoalkanes with aldehydes gives some epoxides and the rearrangement products (ketones) owing to the Lewis acidic nature of the catalyst. Ethyl diazoacetate behaves differently, as 1,2-aryl shift occurs during the reaction. ... 

Syntheses and properties of acetylenic derivatives of pyrazoles 02AHC(82)1. Syntheses of 2-pyrazolines by the reactions of a,/ -unsaturated aldehydes, ketones, and esters with diazoalkanes, nitrile imines, and hydrazines 02JHC1. 

Homologation of carbonyl compounds. The very bulky organoaluminums promote reaction of aldehydes and ketones with diazoalkanes. Aldehydes afford ketones. 

Table 2-1 shows ten types of synthetic process. Methods 1 and 2 are based on aliphatic amines, 3-5 on derivatives of carbonyl compounds, 6 on hydrocarbons with a relatively acidic CH proton, and 7-9 are reactions of diazoalkanes obtained by one of the types 1-6. Reaction 10 involves a diazo ketone, which can be obtained by reaction 9, the first step of the Arndt-Eistert synthesis. 

In the context of ring enlargements by the Tiffeneau rearrangement, we have already mentioned in Section 7.7 the ring enlargement of cyclic ketones by reaction with diazomethane (see Scheme 7-48). This process is, of course, also an electrophilic substitution at the C(a)-atom of a diazoalkane. 

Various Reactions of Monocyclic Thiophens.—In connection with attempts to obtain a better synthesis of 3-thienylmalonic acid, the reaction of diazoalkanes with thiophen has been investigated. However, dimethyl diazomalonate gave the stable ylide (105). Simple diazo-ketones, on the other hand, resulted in... 

A proposed reaction pathway by which ammonia is formed is shown in Scheme 6. After the dissociation of phosphine, attack by another hydrazido complex (e.g., A) to form a bridged species, C, is proposed. Hydrazido complexes such as A are known to be good nucleophiles. For example, they react in acid catalyzed reactions with aldehydes and ketones to form diazoalkane complexes (e.g.. Equations 4 and... 

This reaction has been extended to directly convert aldehydes into -keto esters by reacting with ethyl diazoacetate in the presence of a catalytic amount of SnCl2. In addition, the reaction between diazoalkanes and acyl halides to form a-halomethyl ketones, known as the Nierenstein Reaction, should be considered as another extension of the Schlotterbeck reaction. 

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