Diels-Alder reactions acylnitroso

A type 2 intramolecular /V-acylnitroso Diels-Alder reaction of hydroxamic acid 177 followed by catalytic hydrogenation of the double bond was employed for the synthesis of substituted bridged bicyclic derivative 178, as a single diastereomer (Scheme 75 <2002OL2637>). Cleavage of the N-O bond was performed by reduction with Na(Hg) amalgam and provided m-3,7-disubstituted azocane 9, as a single isomer in 80% yield. 

Diastereoselective acylnitroso Diels-Alder reactions were performed using enantiopure hydroxamic acids derived from camphor and a-amino acids as chiral auxiliaries (Equation 90) <1997JOC3806, 1998T10537, 2003TL4571>. 

The hetero Diels-Alder reaction <01H1591, 01TL5693> and dipolar cycloadditions continue to constitute important approaches to piperidines. Kibayashi and co-workers used an intramolecular acylnitroso Diels-Alder reaction to synthesize (-)-lepadins A,B, and C from an acyclic precursor <01JOC3338>. An intramolecular nitrone cycloaddition was used by Machetti and co-workers to produce both enantiomers of 4-oxopipecolic acid <01T4995>. Their synthesis proceeds from a nitrone bearing an a-methylbenzylamine chiral auxiliary. Noteworthy in this report is the presence of large-scale experimental procedures the nitrone formation and cycloaddition reactions were performed on 285 mmol and 226 mmol scales, respectively. 

Pericycttc Reactions Although a wide variety of ring-expansion processes through pericyclic cyclizations have been described, only a few cycloaddition methods were depicted for the direct generation of medium-ring heterocycles. The most attractive approaches were the [4-1-3] cycloaddition, the 1,3-dipolar cycloaddition of nitrone, and the type-2 intramolecular N-acylnitroso Diels-Alder reaction. 

Scheme 4.22 Synthesis of the tricychc BCD core of stenine by intramolecular Af-acylnitroso Diels-Alder reaction.

Sparks, S. M., Chow, C. P., Zhu, L., Shea, K. J. (2004). Type 2 intramoleculariV-acylnitroso Diels-Alder reaction scope and application to the synthesis of medium ring lactams. Journal of Organic Chemistry, 69, 3025-3035. 

Ozawa T, Aoyagi S, Kibayashi C. Total synthesis of the marine alkaloids (—)-lepadins A, B, and C based on stereo-controlled intramolecular acylnitroso-Diels-Alder reaction. J. Org. Chem. 2001 66(10) 3338-3347. 

Abe, H., Aoyagi, S., and Kibayashi, C. (2000) First total synthesis of the marine alkaloids ( )-fascicularin and ( )-lepadiformine based on stereocontrolled intramolecular acylnitroso-Diels-Alder reaction. J. Am. Chem. Soc., 122, 4583-4-592. 

Development and application of hetero Diels-Alder reactions with participation of amino acid-derived chiral acylnitroso compounds 98T1317. 

Chiral heterocyclic compounds containing vicinal oxygen and nitrogen atoms were achieved by an asymmetric Diels-Alder reaction [111] of chiral acylnitroso dienophiles 111. The latter were prepared in situ from alcohols 110, both antipodes of which are available from camphor, and trapped with dienes (Scheme 2.46). Both the yield (65-94 %i) and diastereoisomeric excess (91-96%) were high. 

Table 4.15 Diels-Alder reactions of acylnitroso compounds...

The nitroso moiety of the N-acylnitroso function is a powerful dienophile and therefore N-acylnitroso compounds are trapped rapidly, especially in an intramolecular reaction, with a diene allowing the Diels Alder reaction to occur also in water, although N-acylnitroso compounds are short-lived in aqueous medium. 

Vogt P. E., Miller M. J. Development and Applications of Amino Acid-Derived Chiral Acylnitroso Hetero Diels-Alder Reactions Tetrahedron 1998 54 1317 1348 Keywords nitroso and acylnitroso dienophlles, befero-Dlels-Alder reaction... 

Aoyagi, S., Tanaka, R., Naruse, M., Kibayashi, C. (1998) Total Synthesis of (—)-Epibatidine Using an Asymmetric Diels-Alder Reaction with a Chiral N-Acylnitroso DienophUe. Journal of Organic Chemistry, 63, 8397-8406. 

The hetero-Diels-Alder reaction has also utilized dienophiles in which both reactive centers are heteroatoms. Kibayashi reported that the intramolecular hetero-Diels-Alder cycloaddition of chiral acylnitroso compounds, generated in situ from periodate oxidation of the precursor hydroxamic acid, showed a marked enhancement of the trans-selectivity in an aqueous medium compared with the selectivity in nonaqueous conditions (Eq. 12.55).125 The reaction was readily applied to the total synthesis of (—)-pumiliotoxin C (Figure 12.5).126... 

An extensive review of the hetero-Diels-Alder reactions of 1-oxabuta-1,3-dienes has been published. Ab initio calculations of the Diels-Alder reactions of prop-2-enethial with a number of dienophiles show that the transition states of all the reactions are similar and synchronous.Thio- and seleno-carbonyl compounds behave as superdienophiles in Diels-Alder reactions with cyclic and aryl-, methyl-, or methoxy-substituted open-chain buta-1,3-dienes.The intramolecular hetero-Diels-Alder reactions of 4-benzylidine-3-oxo[l,3]oxathiolan-5-ones (100) produce cycloadducts (101) and (102) in high yield and excellent endo/exo-selectivity (Scheme 39). A density functional theoretical study of the hetero-Diels-Alder reaction between butadiene and acrolein indicates that the endo s-cis is the most stable transition structure in both catalysed and uncatalysed reactions.The formation and use of amino acid-derived chiral acylnitroso hetero-Diels-Alder reactions in organic synthesis has been reviewed. The 4 + 2-cycloadditions of A-acylthioformamides as dienophiles have been reviewed. ... 

Aliphatic nitroso compounds can be prepared from IV-alkylhydroxylamines by oxidation with bromine, chlorine or sodium hypochlorite in weakly acidic solution, by reaction with potassium dichromate in acetic or sulfuric acid, and by oxidation with yellow mercury(II) oxide in suspension in an organic solvent. Silver carbonate on (Telite has also been used to prepare aliphatic nitroso compounds, such as ni-trosocyclohexane, in high yield from the corresponding hydroxylamines. Aqueous sodium periodate and tetraalkylammonium periodates, which are soluble in organic solvents, are the reagents most commonly used for the oxidation of hydroxamic acids and / -acylhydroxylamines to acylnitroso compounds (40). These compounds are rarely isolated, but are useful as highly reactive dienophiles in the Diels-Alder reaction. ... 

Stereoselective Diels-Alder reactions have been performed variously, using chirally modified sulfines as dienophiles, chiral ynamines, SMP enamines, SMP acrylamides, and the in situ preparation of SMP A-acylnitroso dienophiles. The [2 + 2] cycloaddition reactions of chiral keteniminium salts obtained from SMP amides with alkenes have been studied. ... 

Similarly, acylnitioso compounds are recognized for their 27r participation in Diels-Alder reactions with dienes and these observations have found substantial application (Chapter 4.2). In addition, recent efforts have detailed the apparent 4ir participation of an acylnitroso compound in a Diels-Alder reaction with a cyclopentadiene that suggests their potentially useful 47r participation in LUMOdiene-controlled Diels-Alder reactions (equation 14). ... 

Acylnitroso alkenes produced via rDA reactions are key intermediates in the synthesis of alkal-oids. The acylnitroso alkene intermediate (167) that is generated from anthracene adduct (166) can react by an intramolecular ene reaction, resulting in the formation of hydroxamic acid (168). If the acylnitroso alkene is produced in the presence of a diene, an intramolecular Diels-Alder reaction can occur to give a 1,2-oxazine derivative such as (170) as shown in equation (76). ... 

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