SNAr reactions of β-substituted porphyrins and the synthesis of meso substituted tetrabenzoporphyrins
作者:Mathias O. Senge、Ines Bischoff
DOI:10.1016/j.tetlet.2003.12.121
日期:2004.2
suitable for further transformations with residues such as –p-C6H5Br, –p-C6H5–CCH, –p-C6H5–NH2 or –(CH2)3–CHCH2. Similar reactions of tetrabenzoporphyrin with alkyllithium reagents afforded the first entry into meso mono- and dialkylsubstituted tetrabenzoporphyrins while reaction of bicyclo[2.2.2]oct-type masked isoindole precursors with LiR followed by in situ retro-Diels–Alder reaction also afforded
- 2,3,7,8,12,13,17,18-八乙基卟啉与含有官能团的容易产率中位取代的适合于与残基如进一步转化衍生物LIR试剂的反应p -C 6 H ^ 5 BR, - p - C 6 H 5 –CCH,– p -C 6 H 5 –NH 2或–(CH 2)3 –CHCH 2。四苯并卟啉与烷基锂试剂的类似反应提供了首先进入内消旋的单和二烷基取代的四苯并卟啉,而双环[2.2.2]八型掩蔽的异吲哚前体与LiR的反应,然后原位逆Diels-Alder反应也提供了5-高纯度的苯基和5,10-二苯基四苯并卟啉。
Facile access to the ABC ring system of the taxane diterpenes via anionic oxy-Cope rearrangements
functionalized by introducing a double bond conjugated to the carbonyl group (27a→40); moreover, oxygen functionality at C(13) could be introduced by allylic oxidation (28a→41 and 40→42). The enolates produced in situ by the anionic oxy-Cope rearrangement could be trapped by alkylating agents. These alkylations were highly stereoselective when the ketone enolate was trisubstituted as exemplified by
The intramolecularcyclization reaction of primary or secondary alkenylzincs leads to a cyclopentylmethylzinc derivatives in a totally regiospecific 5-exo-trig cyclization in the presence of a highly sensitive function.
products 6 and/or 7 are observed if the nitronates, generated from the substrate 1a, are added to 85% aqueous H2SO4 but only the hydrolyzed carboxylic acids 9 are generated when the β-nitrostyrenes 2 are reacted with Grignard reagents and worked up under the same condition. The nitrile oxides 7 can undergo 1,3-dipolar cycloaddition with alkenes or alkynes to generate 2-isoxazolines or isoxazoles. A one-pot
β型硝基苯乙烯1或2与格氏或有机锂试剂反应在乙醚或THF溶液由1,4-加成中间nitronates以产生甲。当用稀盐酸处理A时,获得高产率的硝基烷3(和肟4)或5。当将中间体A缓慢加入到冰冷的浓氢卤酸中时,可以分离出羟甲酰卤6、8或一氧化氮7。如果从基材1a产生的硝酸盐观察到相同的产物6和/或7。将β-硝基苯乙烯2加入到85%的H 2 SO 4水溶液中,但是当β-硝基苯乙烯2与格氏试剂反应并在相同条件下进行后处理时,仅产生水解的羧酸9。腈氧化物7可与烯烃或炔烃进行1,3-偶极环加成反应以生成2-异恶唑啉或异恶唑。据报道,通过分子内一氧化氮-烯烃环加成反应可以一锅合成[n,3,0]双环(n = 3或4)化合物23-27。
Chirospecific synthesis of trans-2,5-disubstituted pyrrolidines via stereoselective addition of organocopper reagents to N-acyliminium ions.
作者:Lars-G. Wistrand、Marco Skrinjar
DOI:10.1016/s0040-4020(01)87047-2
日期:1991.1
Reaction of the N-acyliminium ion precursor 1a (derived from S-proline via anodic methoxylation) with RCu in the presence of BF3·Et2O gives preferentially the trans adducts 2 (trans:cis ≥96:4). Using such a procedure, a general synthetic route to (2R, 5R)-trans-2,5-dialkylpyrrolidines has been developed, as exemplified by the chirospecific syntheses of the ant feromones trans 5-butyl-2-heptylpyrrolidine