Isopropenyl formate

Isopropenyl formate is a useful compound for the formylation of primary and secondary amines. 

As in 0-52 hydrazides and hydroxamic acids can be prepared from carboxylic esters, with hydrazine and hydroxylamine, respectively. Both hydrazine and hydroxylamine react more rapidly than ammonia or primary amines (the alpha effect, p. 351). Imidates RC(=NH)OR give amidines RC(=NH)NH2. Lactones, when treated with ammonia or primary amines, give lactams. Lactams are also produced from y- and 8-amino esters in an internal example of this reaction. Isopropenyl formate is a useful compound for the formylation of primary and secondary amines,897... 

Isopropenyl formate formylates amines under mild neutral conditions. ... 

With aldehydes, primary alcohols readily form acetals, RCH(OR )2. Acetone also forms acetals (often called ketals), (CH2)2C(OR)2, in an exothermic reaction, but the equiUbrium concentration is small at ambient temperature. However, the methyl acetal of acetone, 2,2-dimethoxypropane [77-76-9] was once made commercially by reaction with methanol at low temperature for use as a gasoline additive (5). Isopropenyl methyl ether [116-11-OJ, useful as a hydroxyl blocking agent in urethane and epoxy polymer chemistry (6), is obtained in good yield by thermal pyrolysis of 2,2-dimethoxypropane. With other primary, secondary, and tertiary alcohols, the equiUbrium is progressively less favorable to the formation of ketals, in that order. However, acetals of acetone with other primary and secondary alcohols, and of other ketones, can be made from 2,2-dimethoxypropane by transacetalation procedures (7,8). Because they hydroly2e extensively, ketals of primary and especially secondary alcohols are effective water scavengers. 

Reaction conditions depend on the reactants and usually involve acid or base catalysis. Examples of X include sulfate, acid sulfate, alkane- or arenesulfonate, chloride, bromide, hydroxyl, alkoxide, perchlorate, etc. RX can also be an alkyl orthoformate or alkyl carboxylate. The reaction of cycHc alkylating agents, eg, epoxides and a2iridines, with sodium or potassium salts of alkyl hydroperoxides also promotes formation of dialkyl peroxides (44,66). Olefinic alkylating agents include acycHc and cycHc olefinic hydrocarbons, vinyl and isopropenyl ethers, enamines, A[-vinylamides, vinyl sulfonates, divinyl sulfone, and a, P-unsaturated compounds, eg, methyl acrylate, mesityl oxide, acrylamide, and acrylonitrile (44,66). 

Isopropenyl acetate and allyl chloride behave similarly. In the polymerization of the latter monomer degradative chain transfer occurs more readily by removal of the chlorine atom to yield the unsubstituted allyl radical CH2—CH—CH2, which manages to add monomer occasionally. This is indicated by the formation of about three polymer molecules, having an average degree of polymerization of six units, for each molecule of benzoyl peroxide decomposing. 

Entry 7 illustrates reaction conditions that were applicable to formation and rearrangement of an isopropenyl allylic ether. The tri-isopropylaluminum is thought to both catalyze the sigmatropic rearrangement and reduce the product ketone. 

Intramolecular oxonium ylide formation is assumed to initialize the copper-catalyzed transformation of a, (3-epoxy diazomethyl ketones 341 to olefins 342 in the presence of an alcohol 333 . The reaction may be described as an intramolecular oxygen transfer from the epoxide ring to the carbenoid carbon atom, yielding a p,y-unsaturated a-ketoaldehyde which is then acetalized. A detailed reaction mechanism has been proposed. In some cases, the oxonium-ylide pathway gives rise to additional products when the reaction is catalyzed by copper powder. If, on the other hand, diazoketones of type 341 are heated in the presence of olefins (e.g. styrene, cyclohexene, cyclopen-tene, but not isopropenyl acetate or 2,3-dimethyl-2-butene) and palladium(II) acetate, intermolecular cyclopropanation rather than oxonium ylide derived chemistry takes place 334 ). 

DIASTEREOSELECTIVE FORMATION OF TRANS-1,2-DISUBSTITUTED CYCLOHEXANES FROM ALKYLIDENEMALONATES BY AN INTRAMOLECULAR ENE REACTION DIMETHYL (1 R,2 R,5 R)-2-(2 -ISOPROPENYL-5 -METHYLCYCLOHEX-1 -YL)-PROPANE-1,3-DIOATE... 

These isomers resulted from the non-stereoselectivity of the initial coupling process typical of the aza-ACE reactions of the 7-isopropylidene-bridged dipolarophile 38, while molecular weight measurements and the presence of an isopropenyl group in the H NMR of each product supported C,A-methano-bridge formation. Such products were considered to arise via the bond reorganisation depicted by the arrows in adduct 156 in which one of the isopropylidene rc-bonds acted as the nucleophile to attack the methylene carbon of the adjacent A-methoxymethyl group. 

Very recently, the formation of azabutadienylosmium complexes through transfer of the isopropenyl group of a phosphine ligand to benzonitriles on a Cp-Os metal complex has been reported (Scheme 79).373... 

Admittedly, we are not surprised that the decomposition enthalpies of styrene and 2-vinylnaphthalene peroxides are close to each other, as are those of the isomeric isopropenyl species. There is a rather rehable constant enthalpy of formation difference between phenyl and naphthyl derivatives, and as a corollary, a near-equaUty of the enthalpies of formation of 1- and 2-naphthyl derivatives, cf. the combined calculational and calorimetric studies of M. V. Roux, M. Temprado, R. Notario, S. P. Verevkin, V. N. Emel yanenko, D. E. DeMasters and J. F. Liebman, Mol. Phys., 102, 1909 (2004) and references cited therein. It is perhaps more surprising that the a-methyl group on the unsaturated moiety (vinyl -> isopropenyl) causes such a small change. 

From the decomposition mechanism and the products formed it can be deduced that DCP primarily generates cumyloxy radicals, which further decompose into highly reactive methyl radicals and acetophenone, having a typical sweet smell. Similarly, tert-butyl cumyl peroxide (TBCP) forms large quantities of acetophenone, as this compound still half-resembles DCP. From the decomposition products of l-(2-6 rt-butylperoxyisopropyl)-3-isopropenyl benzene ( ), it can be deduced that the amount of aromatic alcohol and aromatic ketone are below the detection limit (<0.01 mol/mol decomposed peroxide) furthermore no traces of other decomposition products could be identified. This implies that most likely the initially formed aromatic decomposition products reacted with the substrate by the formation of adducts. In addition, unlike DCP, there is no possibility of TBIB (because of its chemical structure) forming acetophenone. As DTBT contains the same basic tert-butyl peroxide unit as TBIB, it may be anticipated that their primary decomposition products will be similar. This also explains why the decomposition products obtained from the multifunctional peroxides do not provide an unpleasant smell, unlike DCP [37, 38]. 

Boc-B-Ala-D-O-Leu-ODpm General Procedure for Depsipeptide Formation Using Isopropenyl Chloroform ate 1411... 

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