Acyl iodides in organic synthesis: VIII. Reactions with amino acids

Reactions of acyl iodides RCOI (R=Me, Ph) with glycine, β-alanine, and γ-aminobutyric acid were investigated. The reaction proceeded easily at room temperature without solvent involving both functional groups H₂N and COOH. The prevalence of one of the reaction directions depends on the acidity of the amino acid. The more acidic glycine (pК_a 2.4) reacts with RCOI affording mainly N-acylated product, whereas β-alanine (pК _a 3.60) and especially γ-aminobutyric acid (pК_a 4.06) are predominantly involved into exchange iodination furnishing the corresponding aminoacyl iodides.     

Acyl iodides in organic synthesis: XII. Reactions with organosilicon amines

Reactions were investigated between acyl iodides RCOI (R = Me, Ph) and organosilicon amines of two classes: trimethyl(diethylamino)silane, dimethyl-bis(diethylamino)silane, and hexamethyldisilazane on the one hand, and 3-aminopropyl(triorganyl)silanes H₂N(CH₂)₃SiX₃ (X = Et, EtO) on the other hand. The reaction of RCOI with trimethyl(diethylamino)silane Me₃SiNEt₂ occurred with a cleavage of the Si-N bond and the formation of N,N-diethylacet- or -benzamides and trimethyliodosilane separated in a mixture with hexamethyldisiloxane. At the reaction of acyl iodides RCOI (R = Me, Ph) with dimethyl-bis(diethylamino)silane in the ratio 2:1 in benzene solution both Si-N were ruptured leading to the diethylamide of the corresponding acid and dimethyldiiodosilane. The main product of the reaction of acetyl iodide with hexamethyldisilazane at the molar ratio 2:1 was diacetylimide (MeCO)₂NH. This reaction can be recommended as a simple and convenient preparation procedure for diacylimides. The exothermal reaction of the acetyl iodide with 3-aminopropyl(triethyl)- and -(triethoxy)silanes at the molar ratio of the reagents 1:1 without solvent resulted in quaternary ammonium salts, hydroiodides of the corresponding acetylamides I^?MeCON⁺H₂(CH₂)₃SiX₃ (X = Et, OEt).     

Acyl iodides in organic synthesis. Reaction of acyl iodides with triphenylethoxy- and triphenylhydroxysilane

The reaction of triphenylethoxysilane with acetyl or benzoyl iodide led to the formation of triphenyliodosilane and ethyl ester of the corresponding carboxylic acid. Triphenyliodosilane formed also in the reaction of triphenylsilanol with benzoyl iodide. These reactions comprise the new simplest method of preparation of the triphenyliodosilane (yield over 60%). The reaction product of triphenylhydroxysilane and acetyl iodide is triphenylacetoxysilane. The reactions of the studied acyl iodides with triphenylhydroxysilane is the first example of different regioselectivity of acetyl iodide and benzoyl iodide in reactions with organic and organoelemental compounds.     

Acyl iodides in organic synthesis: XIII. Reaction of acyl iodides with nitrogen-containing heteroaromatic compounds

Reactions of acetyl iodide with pyridine at room temperature and with quinoline both at 20–25°C and on cooling to −50°C involve dehydrohalogenation of acetyl iodide with formation of ketene and pyridinium or quinolinium iodides. The reaction of acetyl iodide with pyridine at −5 to −50°C led to the formation of N-acetylpyridinium iodide. Benzoyl iodide reacted with both pyridine and quinoline at both −50°C and at 20–25°C to form stable N-benzoylpyridinium and N-benzoylquinolinium iodides. The reaction of pyrrole with acetyl iodide under analogous conditions was accompanied by polymerization.     

Acyl iodides in organic synthesis: VII. Reactions with trialkyl(alkynyl)silanes,-germanes, and-stannanes

Reactions of acyl iodides R¹COI (R¹=Me, Ph) with trialkyl(alkynyl)silanes,-germanes, and stannanes (R²C≡CMR ₃ ³ ; M=Si, Ge, Sn) were studied. Acyl iodides reacted with the germanium and tin derivatives with cleavage of the M-C_sp bond and formation of the corresponding trialkyl(iodo)germanes and-stannanes R ₃ ³ MI (M=Ge, Sn) and alkynyl ketones R¹C(O)C≡CR² and R¹C(O)C≡CC(O)R¹. By contrast, the reaction of acetyl iodide with ethynyl(trimethyl)silane gave only a small amount of 1,2-diiodovinyl(trimethyl) silance as a result of iodine addition at the triple bond. Bis(trimethylsilyl)ethyne failed to react with acetyl iodide.     

Acyl iodides in organic synthesis. Reaction of acetyl iodide with thiols

The direction of reactions of acetyl iodide with aliphatic, aromatic, and heterocyclic thiols is determined by the thiol acidity and steric factors. Acetyl iodide reacted with aliphatic thiols, including trialkylsilylsubstituted derivatives R(CH₂) _n SH (R = Me, n = 3; R = Me₃Si, n = 3; R = Et₃Si, n = 2), to give the corresponding ethanethioates R(CH₂) _n SCOMe. Benzenethiol was oxidized with acetyl iodide to diphenyl disulfide. The reaction of acetyl iodide with 2-sulfanylethanol afforded 2-(2-iodoethyldisulfanyl)ethyl acetate as a result of three consecutive-parallel processes: acylation, iodination, and oxidation of the initial compound. 1,3-Benzothiazole-2-thiol reacted with acetyl iodide only at the nitrogen atom to give quaternary salt, whereas the SH group remained intact.     

Acyl iodides in organic synthesis. reaction of acetyl iodide with Dialkyl sulfides and disulfides

Reactions of acetyl iodide with dialkyl and dialkenyl sulfides RSR (R = Et, Bu, CH₂=CH, CH₂=CHCH₂) and with disulfides RSSR (R = Pr, C₆H₁₃, PhCH₂) were studied. Dialkyl sulfides reacted with MeCOI to give the corresponding alkyl ethanethioates and alkyl iodides as a result of cleavage of the S-C bond. The reactions of acetyl iodide with divinyl and diallyl sulfides involved addition across the double bond and subsequent polymerization of 1-alkenylsulfanyl-2(3)-iodoalkyl methyl ketones. Dialkyl disulfides RSSR (R = Pr, C₆H₁₃) and dibenzyl disulfide reacted with acetyl iodide via cleavage of the S-S bond to produce the corresponding ethanethioates and organylsulfenyl iodides. The latter underwent disproportionation to form the initial disulfide and molecular iodine.     

Acyl iodides in organic synthesis: IX. Cleavage of the Si-O-C and Si-O-Si moieties

Reactions of acyl iodides RCOI (R = Me, Ph) with organosilicon compounds involve cleavage of the Si-O-C and Si-O-Si fragments. Acetyl iodide reacts with alkyl(alkoxy)silanes with evolution of heat, and cleavage of the Si-O bond results in the formation of oligo-or polysiloxanes, alkyl iodides, and alkyl acetates. 1,3-Diacetoxytetramethyldisiloxane is formed in the reaction of acetyl iodide with dimethoxy(dimethyl)silane. Acyl iodides readily react with 1-ethoxysilatrane to give 1-acyloxysilatranes as a result of cleavage of the C-O bond. The reaction of acetyl iodide with hexaethyldisiloxane yields triethylsilyl acetate and triethyliodosilane, while in the reaction with octamethyltrisiloxane iodo(trimethyl)silane and dimethyl(trimethylsiloxy)silyl acetate are obtained.     

Acyl iodides in organic synthesis: XI. Unusual N-C bond cleavage in tertiary amines

Acyl iodides reacted with excess primary and secondary amines in a way similar to acyl chlorides, yielding the corresponding carboxylic acid amide and initial amine hydroiodide. Reactions of tertiary amines with acyl iodides were accompanied by cleavage of the N-C bond with formation of the corresponding N,N-di(hydrocarbyl)carboxamide and alkyl iodide. In the presence of excess tertiary amine the latter was converted into quaternary tetra(hydrocarbyl)ammonium iodide.     

Acyl iodides in organic and organoelement chemistry

This review is focused on our and literature data on reactions of acyl iodides RC(O)I with organic (alcohols, ethers, esters, carboxylic acids, amino acids, tertiary amines, nitrogen heterocycles, carbamides, thiocarbamides, and thiols) and organoelement compounds (alkoxy silanes, siloxanes, silylamines, silazanes, silicon-containing amines, and ethynyl silanes, germanes, and stannanes). Photolysis of acyl iodides in arene medium yields a-diketones, products of photochemical Friedel-Crafts acylation and iodination of arenes, and polyarylenation.     

Acyl iodides in organic synthesis. Reactions with morpholine,piperidine, and <Emphasis Type=Italic>N</Emphasis>-hydrocarbylpiperidines

Acyl iodides RCOI (R = Me, Ph) reacted with morpholine and piperidine to give the corresponding N-acyl derivatives and morpholine or piperidine hydroiodides. Reactions of acyl iodides with N-methyl- and N-ethylpiperidines involved cleavage of the exocyclic R-N bond with formation of N-acylpiperidine and alkyl iodide and were accompanied (to insignificant extent) by cleavage of the endocyclic N-C bond, leading to N-alkyl-N-(5-iodopentyl)acylamides. In the reaction of acetyl iodide with N-phenylpiperidine, the main process was cleavage of just endocyclic N-C bond to produce N-(5-iodopentyl)-N-phenylacetamide and its dehydroiodination product, N-(pent-4-en-1-yl)-N-phenylacetamide. Analogous reaction with benzoyl iodide afforded N-(5-iodopentyl)-N-phenylbenzamide in a poor yield.     

Reactions of N-bromohexamethyldisilazane with triorganylsilanes

Reactions of N-bromohexamethyldisilazane (Me₃Si)₂NBr with Si-H compounds of the general formula RR′₂SiH yield up to 90% of unsymmetrical disilazanes (Me₃Si)₂NSiRR′₂ and bromotrimethylsilane. An unexpected solvent effect on the reaction conditions is revealed: In benzene the products are formed already on mixing, whereas in cyclohexane, under UV irradiation only.     

Acyl Iodides in Organic Synthesis: I. Reactions with Alcohols

Reaction of acyl iodides RC(O)I (R = Me, Ph) with alcohols R'OH (R' = Me, Et, i-Pr, t-Bu, CH₂ = CHCH₂, HCCCH₂) provides in the corresponding organyl iodides R'I. Unlike that 2-chloroethanol and phenol (R' = CH₂CH₂Cl, Ph) react with RC(O)I in the same way as with acyl chlorides yielding esters RCO₂R'. This reaction path occurs partially also with methanol and ethanol.     

Acyl Iodides in Organic Synthesis: VI. Reactions with Vinyl Ethers

Reactions of acetyl iodide with butyl vinyl ether, 1,2-divinyloxyethane, phenyl vinyl ether, 1,4-di-vinyloxybenzene, and divinyl ether were studied. Vinyl ethers derived from aliphatic alcohols (butyl vinyl ether and 1,2-divinyloxyethane) react with acetyl iodide in a way similar to ethyl vinyl ether, i.e., with cleavage of both O–Csp2 and Alk–O ether bonds. From butyl vinyl ether, a mixture of vinyl iodide, butyl acetate, vinyl acetate, and butyl iodide is formed, while 1,2-divinyloxyethane gives rise to vinyl iodide, vinyl acetate, and 2-iodoethyl acetate. The reaction of acetyl iodide with divinyl ether involves cleavage of only one O–Csp2 bond, yielding vinyl acetate and vinyl iodide. In the reactions of acetyl iodide with phenyl vinyl ether and 1,4-divinyloxybenzene, only the O–CVin bond is cleaved, whereas the O–CAr bond remains intact.     

Reactions of piroxicam with alkyl iodides

Alkylation of piroxicam with a homologous series of alkyl iodides gave reversibly formed O-alkyl products 1 as well as unexpected, irreversibly formed zwitterionic compounds 2 , alkylated on the pyridine nitrogen, and O,N-bis-alkyl products 3 . Proof of structure was accomplished by nmr and X-ray crystal analysis. Product distribution ratios were determined by hplc and are explained by the Hard-Soft Acid-Base principle.     

Acyl Iodides in Organic Synthesis: II. Reactions with Acyclic and Cyclic Ethers

Reaction of acyl iodides RCOI (R = Me, Ph) was studied with acyclic and cyclic ethers (Et₂O, MeCHCH₂(O), ClCH₂CHCH₂(O), THF, O(CH₂CH₂)₂O, EtOCH₂CH₂OH, EtOCH = CH₂, PhOEt]. The reaction occurred with the rupture of one or two CO bonds furnishing the corresponding iodides and esters.     

Acyl Iodides in Organic Synthesis: V. Reactions with Carboxylic Acid Esters

Acyl iodides react with alkyl, alkenyl, and aralkyl esters derived from saturated, unsaturated, and aromatic mono- and dicarboxylic acids in the absence of a catalyst. The reaction involves cleavage of the OR bond and formation of organic iodide RI (including CH₂=CHI) and one or two symmetric carboxylic acid anhydrides. Phenyl acetate reacts with benzoyl iodide to give acetyl iodide and phenyl benzoate as a result of cleavage of the (O=)C–O bond. The reaction of diethyl fumarate with acetyl iodide is accompanied by cis– trans isomerization to afford maleic anhydride. In the reactions of acetyl iodide with diethyl oxalate and diethyl malonate, CO and CO₂ and CO₂ and polyketene are formed, respectively, in addition to ethyl iodide and acetic anhydride. Ethyl esters of strong organic acids, e.g., ethyl trihaloacetates, failed to react with acyl iodides under analogous conditions.     

Reactions of hypervalent iodine reagents with palladium: mechanisms and applications in organic synthesis

The unique reactivity of hypervalent iodine reagents with Pd0 and PdII complexes has been exploited for a variety of synthetically useful organic transformations. For example, IIII reagents have been used in place of aryl halides for diverse Pd-catalyzed C-C and C-heteroatom bond-forming cross-coupling reactions. In addition, these reagents have found application in Pd-catalyzed oxidation reactions, including the oxidative functionalization of C-H bonds and the 1,2-aminooxygenation of olefinic substrates. This review discusses both the synthetic utility and the interesting mechanistic features of these transformations.