New Synthesis of benzocyclobutene

Abstract

55% yield: mp 42-43°( lit.6 mp 42-43°); ir (CC14) 1710 cm-1 (C=0); nmr (CC14) 1.15 (s, 6), 2.9 (s, 2), 7.3 (m, 4). l-ierf-Butylethynyl-2,2-dimethylindan-l-ol was prepared as described earlier3 for the general synthesis of tertiary propargyl alcohols by addition of iert-butylethynyllithium to 2,2-dimethyl-1-indanone. Distillation afforded the alcohol in 82% yield (99-100°at 0.5 mm): ir (neat) 3460 cm-1 (O-H), 2250 cm-1 (C=C); nmr (CC14) 1.0 (s, 3), 1.15 (s, 3), 1.23 (s, 9), 2.02 (s, 1), 2.55 (s, 1), 2.78 (s, 1), 7.05 (m, 4).l-(terf-Butylchlorovinylidene)-2,2-dimethylindan (2) was prepared according to the general procedure for the preparation of chloroallenes by Jacobs and Fenton.7 After three successive distillations from a small amount of sodium borohydride to remove unreacted alcohol, the desired chloroallene was obtained in 23% yield: bp 96-100°at 0.3 mm; ir (neat) 1945 cm-1 (C= C=C); nmr (CC14) S 1.22 (s, 9), 1.29 (s, 6), 2.86 (s, 2), 7.08 (m, 4).

Selective halogen-lithium exchange in bromophenylalkyl halides

“…Scheme I -CH.CH.-+ (Vi 6 (30%) 7 (37%) This was unexpected in view of the earlier report3 which suggested that halogen-metal exchange occurred at the aryl halide function in a similar reaction with p-bromoben-Scheme II oc CHoCl Br -100 "0* CH2C1 Li + zyl bromide. When excess (2 equiv) of n-butyllithium was employed the product was bibenzyl, the product expected by complete halogen-metal exchange in 3 prior to the addition of water.…”

“…Samples of 9 in the tetrahydrofuran-hexane solvent mixture were allowed to warm to room temperature prior to decomposition with water. 6 The product was pro- ß-(o-Bromophenyl)ethyl Bromide (14). Aryl halogenmetal exchange by reaction of 14 with n-butyllithium is selective at -100 °C; the lithio derivative 15 is formed rapidly (approximately 5 min) and can be elaborated as shown in Scheme III.…”

Benzocyclobutene in polymer synthesis. II. Solid state diels–alder polymerization utilizing an in situ generated diene and an alkyne

“…EXPERIMENTAL 4-Bromophthalic anhydride was prepared from the alkaline bromination of phthalic anhydride, followed by cyclodehydration of the crude 4-bromophthalic anhydride in refluxing acetic acid.ll 4-Aminobenzocyclobutene was prepared according to procedures (with some modifications) described in the literature. [12][13][14][15] Triethylamine was purified by distillation in the presence of barium oxide under N,. Dry dimethyl sulfoxide (DMSO) was distilled from calcium hydride under reduced pressure.…”

Recent chemistry of benzocyclobutenes

“…4 A later modi®cation has enabled large scale preparation of the parent BCB via two step 1,4-elimination and reductive dehalogenation. 20 Polysubstituted trichloromethylbenzenes, when warmed above their melting point, lose HCl to give 1,1-dichlorobenzocyclobutenes (Scheme 4). 21 This method has been extended and improved for the large scale preparation of BCB 1 under¯ash vacuum pyrolysis (FVP) (Scheme 5).…”