N. Yu. Kuznetsov

Construction of nitrogen bicyclic and cage compounds with the use of allylic organoboranes

It is shown that reactions of triallylborane with pyrrole, pyridines, isoquinolines, lactams, 1-pyrroline, and acetylenes offer versatile methodology for the construction of various bicyclic and polycyclic nitrogen compounds, some of which are skeletally related to important classes of alkaloids. Optically active 3-borabicyclo[3.3.1]non-6-enes are useful precursors for synthesis of chiral 3-aza- and 3-thiabicyclo[3.3.1]non-6-enes, as well as derived chiral cyclohexenoid systems. The convenient methodology for the transformation of 1-boraadamantanes into 1-azaadamantanes is also discussed.

Synthesis of bridged azabicycles from isoquinolines via a tandem of allylboration and intramolecular metathesis

A method for the synthesis of bridged azabicyclic compounds from isoquinolines was developed. The method is based on a combination of allylboration and ruthenium-catalyzed intramolecular metathesis. Reductive 1,3-diallylation of bromoisoquinolines with triallylborane gave trans-1,3-diallyl-1,2,3,4-tetrahydroisoquinolines. When heated with triallylborane, these compounds yielded mixtures of cis-and trans-isomers in the ratio ∼1: 1. The structure of cis-1,3-diallyl-5-bromo-1,2,3,4-tetrahydroisoquinoline was confirmed by X-ray diffraction analysis. In a similar way, trans-3-allyl-1-vinyl-1,2,3,4-tetrahydroisoquinoline synthesized by sequential vinylation (with vinyllithium) and allylboration of isoquinoline, yielded a mixture of cis-and trans-isomers in the ratio 1.6: 1. Intramolecular metathesis reactions of N-Boc derivatives of cis-isomers in the presence of the Grubbs catalyst (2.0–2.5 mol.%) afforded 7,8-benzo-10-azabicyclo[4.3.1]dec-2-enes or 7,8-benzo-9-azabicyclo[3.3.1]non-2-ene in nearly quantitative yields.

Ruthenium-catalyzed intramolecular metathesis of dienes and its application in the synthesis of bridged and spiro azabicycles

The review presents a historical excursion into catalytic alkene metathesis, covering the problems of history of the discovery of this process, as well as investigations on the properties, structure and reactivity of the most popular ruthenium catalysts for metathesis, mechanism of their action and decomposition. The main part covers studies devoted to the syntheses of bridged azabicyclic and 1-azaspirocyclic compounds comprising the intramolecular metathesis of dienes as the key step. The formation of a bicyclic skeleton of a series of natural bridged (cocaine, ferruginine, calystegines, and anatoxin-a) and spiro (pinnaic acids, halichlorine, hystrionicotoxin, and cephalotaxine) azabicycles, as well as their analogues and compounds with larger rings is demonstrated. The methods for the synthesis of diene precursors and the conditions for final assembling of the bicyclic compounds are considered in detail. The generalization of the literature data allows one to efficiently carry out the mentioned process taking into account the most important features. The bibliography includes 129 references.

Synthesis of 8,9-(1,3-benzodioxolo-5,6)-5-azatricyclo[8.2.1.01,5]tridec-11-en-6-one. A convenient route to structural analogs of the alkaloid cephalotaxine

A synthetic route to 8,9-(1,3-benzodioxolo-5,6)-5-azatricyclo[8.2.1.01,5]tridec-11-en-6-one structurally isomeric to the pentacyclic cephalotaxine nucleus is suggested. The route is based on the sequence including diallylboration of 2-pyrrolidinone and intramolecular metathesis of the resulting 2,2-diallylpyrrolidine, giving rise to 1-azaspiro[4.4]non-7-ene. This product was N-acylated with 6-bromohomopiperonylic acid chloride and then subjected to intramolecular cyclization according to the Heck reaction.

Synthesis of 6,7-benzo-3-borabicyclo[3.3.1]nonane and its 3-aza analog from 2-allylphenyl(diallyl)borane. intramolecular arylboration of the C=C bond

A method was developed for the synthesis of 6,7-benzo-3-borabicyclo[3.3.1]nonane and 6,7-benzo-3-azabicyclo[3.3.1]nonane derivatives based on intramolecular cyclization of 2-allylphenyl(diallyl)borane. Intramolecular arylboration of the double bond in 1,5-diallyl-2,3-benzo-1-boracyclohexane was carried out for the first time. Conventional oxidation (H2O2-OH−) of 6,7-benzo-3-methoxy-3-borabicyclo[3.3.1]nonane afforded cis-1,3-di(hydroxymethyl) tetralin. The structure of the latter was established by X-ray diffraction analysis.

Functionalization of N-tert-butoxycarbonyl-7-and N-tert-butoxycarbonyl-8-bromo-10-azabicyclo[4.3.1]deca-3,7-dienes. A route to a ferruginine homolog

N-tert-Butoxycarbonyl-7-and N-tert-butoxycarbonyl-8-bromo-10-azabicyclo[4.3.1]deca-3,7-dienes are convenient substrates for further modification using replacement of the Br atom by a cyano group or a Li atom. Treatment of lithium derivatives with dimethylformamide and N-methoxy-N-methylacetamide gave the corresponding α,β-unsaturated aldehydes (67–84%) and ketones (∼70%). Ketone 4b is a direct precursor of a homolog of the alkaloid ferruginine.

Reformatsky-type addition of esters of α-halogeno carboxylic acids to aldehydes and ketones in the presence of Fe(CO)5

Reformatsky-type addition of esters of α-halogeno carboxylic acids to aldehydes and ketones in the presence of Fe(CO)5 and an activating agent (CBrCl3 or I2) afforded the corresponding esters of β-hydroxy acids in good yields. Possible reaction mechanisms are discussed.

Stereoselective dimerization of chiral α-bromoamides promoted by Fe(CO)5

Organic α-bromocarboxylates react with aldehydes and ketones in the presence of Fe(CO)5 (the Reformatsky-type reactions). Unlike them, N-oxazolidinone derivatives of the same acids undergo diastereoselective reductive dimerization to give (2S,3S)-dimers, regardless of the configuration of the α-chiral center in the starting reagent.