Synthesis of 1H‐Cyclopropa[b]naphthalenes via Trapping of o‐Benzoquinodimethanes

Abstract

1H-Cyclopropa[b]naphthalene (10a) and 3-methyl or dimethyl derivatives have been synthesized by interception of appropriately substituted o-quinodimethanes 3 with 1-bromo-2-chlorocyclopropene 5, and subsequent dehydrohalogenation of the adducts. The o-quinodimethane derivatives 3 in turn were obtained from the diynes 7 via base-induced isomerization to bisallenes 8 and thermal electrocyclic ring closure.One of the earliest approaches towards 1 H-cyclopropabenzene (1) consists in cycloaddition of butadiene to a di-or tetrahalogenocyclopropene followed by dehydrohalogenation with base (Scheme 1 ) [l]. In principle, the route may be extended to synthesis of the benzannellated homologues, cyclopropa[b]naphthalenes. However, only 1, l-dichloro-2,7-diphenylcyclopropa[b]naphthalene (2) has been prepared in this way [2], since the o -quinodimethane 3, required for the cycloaddition, was readily available from trans -1,2-diphenylbenzocyclobutene (4) via electrocyclic ring opening [3]. In general, however, the conditions used for generation of o-benzoquinodimethanes are not compatible with the presence of the very sensitive halogenocyclopropenes. Scheme I 4 3 2 Recently, we reported that o -naphthoquinodimethane, generated from o -dipropargylbenzene [4] is intercepted with 1,2-dihalogeno-and tetrahalogenocyclopropenes [5].The adducts can be transformed to cycloprop[b]anthracene and its 1,l-dihalogeno derivatives. Although preliminary experiments with o -benzoquinodimethane (3a) and tetrahalogenocyclopropenes afforded no cycloadducts, we found subsequently that the more reactive 1-bromo-2-chlorocyclopropene (5) [6] is moderately efficient in the cycloaddition to 3a. In this communication, we report the application of the sequence towards an alternative synthesis of 1H-cyclopropa[b]naphthalene (10) [7] and some of its methyl derivatives.

Intramolecular Oxonium Ylide Formation–[2,3] Sigmatropic Rearrangement of Diazocarbonyl-Substituted Cyclic Unsaturated Acetals: A Formal Synthesis of Hyperolactone C

“…TMSCl (4.5 mL, 3.83 g, 35.3 mmol) was added dropwise to a solution of ( Z )-2,3-dimethyl­but-2-ene-1,4-diol (1.64 g, 14.1 mmol) and Et 3 N (5.9 mL, 4.31 g, 42.3 mmol) in CH 2 Cl 2 (80 mL) at 0–5 °C. After stirring for 1.5 h at rt, the reaction mixture was washed with H 2 O (4 × 50 mL) and half sat.…”

“…TMSCl (1.0 mL, 7.9 mmol) was added dropwise to a solution of ( Z )-2-methyl­but-2-ene-1,4-diol (203 mg, 2.0 mmol) and Et 3 N (1.2 mL, 8.6 mmol) in CH 2 Cl 2 (19 mL) at 0 °C. The reaction mixture was stirred at 0 °C for 10 min and then warmed to rt.…”

Syntheses and Properties of Medium-Sized Metacyclophanediynes

“…t -BuOK from Aldrich was used for the isomerization reactions of the metacyclophanediynes and sublimated before use. The acyclic diynes 9 , , 11 , 12 , , 13 , , and 14 4 as well as Schwartz's reagent ( 28 ) were prepared according to the literature. Reactions were monitored either by GC or TLC.…”

“…There are two paths in which the metacyclophanediynes 3 − 8 can be prepared by reacting a dihalogen compound with the dilithium salt of a dialkyne as shown in Scheme . With the exception of 10 all open-chain dialkynes needed for path A are described in the literature. − They can be prepared by reacting the corresponding α,ω-dihalogen compounds 15 − 20 with the lithium acetylide−ethylenediamine complex ( 9 , 13 ) 5,6 or acetylenemagnesium chloride ( 21 ) , ( 11 , 12 , , 14 4 ). With the exception of 11 , which can be isolated in only 30% yield, the yield of the other open-chain alkynes varies from 60% to 80%.…”

Six Low-Lying Isomers of C11H8 Are Unidentified in the Laboratory–A Theoretical Study

“…While several derivatives of 7b H -cyclopenta­[ cd ]­indene ( 10 ) have been isolated elsewhere, − the parent molecule remains elusive, which outlines that it is the kinetic control that governs the formation of a particular molecule in the laboratory. Other low-lying neutral molecules of C 11 H 8 that are synthetically characterized are as follows: 1 H -cyclopropa­[ b ]­naphthalene ( 12 ; see Figure ), , 1 H -cyclopropa­[ a ]­naphthalene ( 13 ), penta-1,3-diyn-1-ylbenzene ( 15 ), , 1-(buta-1,3-diyn-1-yl)-4-methylbenzene ( 20 ), , 1-(buta-1,3-diyn-1-yl)-2-methylbenzene ( 22 ), , 1-ethynyl-2-(prop-1-yn-1-yl)­benzene ( 28 ; see Figure ), , 1,4-diethynyl-2-methylbenzene ( 31 ), 1,3-diethynyl-5-methylbenzene ( 33 ), 1,2-diethynyl-4-methylbenzene ( 36 ), and 1,2-diethynyl-3-methylbenzene ( 37 ) …”