Recently bicyclic systems consisting of two fused annulene rings (annulenoannulenes) have received considrable attention. We have reported the synthesis of tetra-t-butylhexakisdehydro[lZ.l2.4] [18]annuleno[l8]annulene (1) and tetrat-butyltrisdehydro[lO.lO.2][14]annuleno[l4]annulene (2) consisting of two tetrakisdehydro[l8]and bisdehydro[l4]annulenes, respectively. Also the synthsis of annulenoannulenes made up of two ortho fused bisdehydroannulene derivatives has been reported by T. M. Cresp and F. Sondheimer (3). We have extended our work to the synthesis of trisdehydro[4m-2.4n-2.2]-[4n+2]annuleno[4m+2]annulenes. In this communication, we wish to report the synthesis of trisdehydro[l4.14.2][18]annuleno[l8]annulene (m=n=4, XIII) and the synthesis of trisdehydro[l4.10.2][14]annuleno[l8]annulene (m=3, n=4) will be reported in the following paper. The addition of t-butylmercaptan (4) to hexen-5-yn-2-one (5) in ethanol in the presence of Triton B yielded 6-t-butylthio-3,5-hexadien-2-one (II, pale yellow needles, mp 58.7%59.5'C, 70%, NMR(60 MHz, CC14): Ha r 4.05 (d, J,b=15); Hb 2.72 (q, Jab=158 Jbc=lO); HC 3.84 (t, Jbc=lO); Hd 3.42 (d, Jcd=lO); CH3 7.81 (s); t-Bu 8.61 (s)). The cis-configuration of 5,6-double bond was revealed by the NMR spectroscopy. Product of the aldol condensation of trimethylsilyl derivative of diennye aldehyde (I) (6) with II was chromatographed on silica gel (Merck), and eluted with ether-benzene (3:97) to give slightly crude pentaenyne ketone (III). The ketone (III) was treated with lithium diethylamide at -82OC in tetrahydrofuran and then with trimethylchlorosilane to yield the trimethylsilyl derivative (IV, yellow tryst., mp 114.0~114.7"C (dec.), M+ 400, 58% based on II, NMR(lOO MHz, CDC13): olefinic T 2.13~3.82 (m); t-Bu 8.57 (s), 8.84 (s); SiMe3 9.75 (s)). The ethynyl alcohol (V) obtained by the reaction of IV with lithium acetylide in tetrahydrofuran (8) was treated without isolation with an aqueous sulfuric acid to give the aldehyde (VI, orange tryst., mp 105.3$106.7ยฐC (de.), M+ 336, 83%, NMR(60 MHz, CC14): CHO r 0.34 (d); olefinic 2.18~3.88 (m); -CECH 6.34 (s); t-Bu 8.84 (s); SiMe3 9.75 (s)). The dimethyl acetal (VII) obtained from VI in the usual way was converted into lithio derivative (VIII) on treatment with butyllithium in tetrahydrofuran at -7a-8OC.