Tetrahedron report number 942 Construction of fused heterocycles by metal-mediated [2þ2þ2] cyclotrimerization of alkynes and/or nitriles Mohamed R. Shaaban a, b , Refat El-Sayed b, c , Ahmed H. M. Elwahy a, * a Chemistry Department, Faculty of Science, Cairo University, Giza, Egypt b Chemistry Department, Faculty of Applied Science, Umm Al-Qura University, Makkah Almukkarramah, Saudi Arabia c Chemistry Department, Faculty of Science, Benha University, Benha, Egypt article info Article history: Received 12 April 2011 Available online 6 May 2011 Contents 1. Introduction ..................................................................................................................... 6095 2. General synthetic approaches for fused heterocycles by metal-mediated [2þ2þ2] cyclotrimerization of alkynes and/or nitriles ................ 6096 3. Specific synthesis of fused heterocycles by metal-mediated [2þ2þ2] cyclotrimerization of alkynes and/or nitriles ........................... 6096 3.1. Fused bicyclic systems ....................................................... ............................................... 6096 3.1.1. Carbocyclic fused heterocycles ........................................................................................ 6096 3.1.2. Benzo fused heterocycles ............................................................................................. 6101 3.1.3. Two fused heterocycles .............................................................................................. 6108 3.2. Fused tricyclic systems ...................................................................................................... 6111 3.2.1. Fused [4e5e6] system: three heteroatom .............................................................................. 6111 3.2.2. Fused [4e6e5] system: one bridgehead heteroatom ................................................................................ 6112 3.2.3. Fused [5e6e5] system: one heteroatom .......................................... .................................... 6112 3.2.4. Fused [5e6e5] system: two heteroatoms [1:1] ......................................................................... 6113 3.2.5. Fused [5e5e6] system: one heteroatom .......................................... .................................... 6113 3.2.6. Fused [5e5e6] system: two heteroatoms [1:1] ......................................................................... 6113 3.2.7. Fused [5e5e6] system: three heteroatoms [1:1:1] .............................................................................. 6113 3.2.8. Fused [6e5e5] system: two heteroatoms [1:1] ......................................................................... 6114 3.2.9. Fused [6e6e5] system: one heteroatom .......................................... .................................... 6115 3.2.10. Fused [5e6e6] system: one heteroatom ......................................... .................................... 6116 3.2.11. Fused [5e6e6] system and larger-membered ring analogues [5e6e7/8/9/10]: two heteroatoms [1:1] ........................ 6116 3.2.12. Fused [5e6e6] system: three heteroatoms [1:1:1] ............................................................................. 6117 3.2.13. Fused [6e6e6] system: one heteroatom ......................................................................................... 6118 3.2.14. Fused [6e6e6] system: one bridgehead heteroatom ............................................................................... 6118 3.2.15. Fused [6e6e6] system: two heteroatoms [1:1] ................................................................................ 6118 3.2.16. Fused [6e6e6] system: three heteroatoms [1:1:1] ........................................ ......................................... 6119 3.2.17. Fused [6e7e6] system: three heteroatoms [1:1] .......................................... .......................................... 6119 3.2.18. Fused [7e6e6] system: three heteroatoms [1:1:1] ................................................................................. 6120 3.2.19. Fused [6e6e9] system: three heteroatoms (in one ring) ................................................................ 6120 3.2.20. Fused heteromacrocycles ................................................. .......................................... 6120 3.3. Fused tetracyclic systems .................................................................................................... 6122 3.3.1. Fused [5e5e6e5] systems: three heteroatoms [1:1:1] .................................................................. 6122 3.3.2. Fused [5e6e6e5] systems: two heteroatoms [1:1] ............................................................................ 6123 3.3.3. Fused [5e6e6e5] systems: three heteroatoms [1:2] ..................................................................... 6123 3.3.4. Fused [5e5e6e6] systems: three heteroatoms [1:1:1] ................................................................... 6124 3.3.5. Fused [5e5e6e6] systems: four heteroatoms [2:1:1] ................................................................... 6124 * Corresponding author. E-mail address: aelwahy@hotmail.com (A.H.M. Elwahy). Contents lists available at ScienceDirect Tetrahedron journal homepage: www.elsevier.com/locate/tet 0040-4020/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.tet.2011.04.096 Tetrahedron 67 (2011) 6095e6130