Reactions of phosphorus azides with activated alkynes - The Journal

K. Darrell. Berlin, S. Rengaraju, Theodore E. Snider, and Nagabhushanam. Mandava. J. Org. Chem. , 1970, 35 (6), pp 2027–2029. DOI: 10.1021/jo00831a0...
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NOTES This solid is insoluble in benzene, carbon tetrachloride, and chloroform and is assumed to be a low molecular weight polymer containing chlorine. Ionic Reaction of Iodobenzene Dichlorides witb Cyclodecenes. -For 10 min oxygen was admitted through a sintered-glass dispersion tube and bubbled into a solution of cyclodecene (0.05 mol) in carbon tetrachloride (30 ml), iodobenzene dichloride (0.05 mol) was added to the solution, and the oxygen flow was continued until the insoluble iodobenzene dichloride had disappeared (approximately 36 hr ). Hydrogen chloride was evolved during the reaction. The solvent was removed by rotary evaporation, the product mixture was distilled at reduced pressure, and the distillate fractions were examined by ir and nmr techniques. Table I summarizes the product distribution data. Some of the distillate fractions were mixtures; a low-boiling fraction contained isomeric chloroiodobenzeness as well as 3chloro-1-cyclodecene, and the dichlorocyclodecane fraction from cis-cyclodecene was a mixture of vicinal and transannular dichlorides.13 These mixtures were not separated satisfactorily, but they were readily analyzed by nmr spectroscopy. Radical Reaction of Iodobenzene Dichlorides with Cyclodecenes.-A mixture of cyclodecene (0.05 mol), carbon tetrachloride (30 ml), and iodobenzene dichloride (0.05 mol), contained in a 100-ml round-bottom flask, was degassed by a freezethaw method to eliminate molecular oxygen. The flask was sealed, and the mixture was stirred with a magnetic stirrer a t room temperature until the iodobenzene dichloride had disappeared (5 hr). Hydrogen chloride was evolved when the flask was opened. The mixture was worked up as described above for the ionic reaction with iodobenzene dichloride. The nmr spectrum of the dichlorocyclodecane fraction indicated that only transannular dichlorides were present.18 Reaction with trans-cyclodecene (but not with cis-cyclodecene) led to the formation of 1.3 g of a white, flocculant solid, which recrystallized from chloroform-methanol as needles which did not melt below 330'. This solid was not examined further. Product Identification. 3-Chloro-1-cyclodecene distilled a t 5155' (0.15 mm): nrnr (DCCls) -5.50 (2 H, C=CH), -4.21 (1 H, HCCl), -2.05 (4 H, CHZCCl and CH&=C), and -1.43 (10 H, CHZCHZCH~), all multiplets. Anal. Calcd for CioH1,C1: C, 69.55; H, 9.92. Found: C, 69.42; H, 10.02. The stereochemistry of the C=C was not determined. The addition product identified as trans-1,2-dichlorocyclodecane, bp 68-72' (0.17 mm), gave an nmr spectrum (DCCla) consistent only with a 1,2 isomer:4* -4.36 (2H, HCCl), -2.08 (4 H, HCCCl), and - 1.57 (12 H, CH2CHzCHz),all multiplets. The signal a t -4.36 was a broad, complex one from which coupling constants could not be discerned, even with decoupling experiments. Partial dehalogenation of a sample of the dichloride with zinc dust in refluxing ethanol, and partial dehydrochlorination by potassium t-butoxide in dimethyl sulfoxide solution (room temperature), produced olefin (787, trans- and 22% ciscyclodecene from zinc reaction; 1-chloro-1-cyclodecene from potassium t-butoxide reaction) and left dichloride whose nmr spectrum was unchanged from that of the starting material. Since the isomeric cis- and trans-1,2-dichlorocyclodecanesare expected to undergo these elimination reactions at different rates, these results are taken to be strong evidence that a single 1,2dichloride was formed in the addition reaction. Since cis-l,2dichlorocyclodecane (synthesized by refluxing a mixture of cisdiol, excess thionyl chloride, and dioxaneI4) is a solid [mp 84.586.5'; nmr (DCCl,) -4.96 (HCCl)], the addition product is trans- 1,2-dichlorocyclodecane. trans-1,6-Dichlorocyclodecane (mp 101-103°) crystallized from a distillation fraction [bp 63-66' (0.10 mm)] from some of the chlorine additions. The nmr spectrum (DCCla) reveals an A : B : X proton ratio of 8:8:2, consistent with a 1,4-, 1,5-, or 1,6-dichloride structure.'" A portion of the dichloride was converted into trans-1,6-bis(phenylthio)cyclodecane,4dmp 101-103" (mixture of truns-1,6-dichloro- and truns-1,6-bis(phenylthio)cyclodecanes, mp =(

(C,H,)2N

CH3

9

ina led to P-N cleavage. Condensation of lb and 2a in the absence of solvent near room temperature (initial mixing near 0" for 2 hr) gave 9 which, via nmr (Table I) examination, appeared to be of high purity. Again, heavy decomposition of 9 ensued when distillation was tried even in a molecular still. Ethoxyacetylene (2b) and la or lb react when heated in the absence of solvent under Nz with heavy tar formation. I n benzene, the condensation is sluggish over 3-4 days with recovery of starting azides and the production of tar. Interestingly, lb and 2b combine in a novel but unknown fashion to give triethyl phosphate

(33%). Likewise, tar and ethyl diphenylphosphinate result from la and 2b. Both of these data are in contrast to that reported for reaction of 2b with ArNa, where a triazole results.lOJ1 Whether or not ethoxyla(11) P. Grunanger, P. Vita Finri, and E. Fabbri, auza. C h i n . nul., BO, 413 (1960).

Experimental Section Reaction of Diphenylphosphinyl Azide (la) with 2a. Preparation of Triazole 3.-To solution of distilled 2a (3.35 g, 0.03 mol) [obtained from Fluka AG, Buchs SG, bp 130-132' (760 mm)l, in dry benzene (15 ml) was added a solution of la12 (7.30 g, 0.03 mol) in dry benzene (15 ml) over 30 min at 60-65' in a dry box under N2. The mixture was then boiled for 3 hr. Cooling to room temperature resulted in a dark brown solution, which was diluted to turbidity with hexane and left overnight, whereupon a white solid separated. The mixture was removed from the dry box and chilled in ice; the filtered solid (5.07 g, 49%) melted at 118-120'. Recrystallization from benzene-petroleum ether gave pure3, mp 120.5-121.5'. Anal. Calcd for CIDHZ~N~OP: N, 15.81; P, 8.74. Found: N, 15.55; P, 8.74. Hydrolysis of Triazole 3 .-The triaaole 3 (354 mg, 1 .O mmol) was stirred at room temperature with 5% HC1 (20 ml) for 30 min, and the mixture was poured into saturated NaHC08 solution. Ether extracts of the aqueous mixture were dried (MgSO,) and the solvent was evaporated to give 150 mg (98%) of 4. Distillation gave 4, pure by tlc and nmr, bp 60-70' (0.25 mm). Anal. Calcd for C7H1rN~: N , 36.33. Found: N, 35.94. Acidification with dilute HC1 of the aqueous mixture precipitated 5 (191 mg, 87%), identified by mixture melting point with an authentic sample. Reaction of Diethyl Phosphorazidate (lb) with Za.-To a solution of 2a (2.22 g, 0.02 mol) in dry benzene (10 ml) over a 1-hr period was added lb (3.58 g, 0.02 mol) under Nz. The temperature rose to 44' and fell to 27" within the next 40 min. After another 0.5 hr, the solvent was removed to give 5.5 g of a dark liquid. Distillation at 120-130" (0.005 p ) resulted in extensive decomposition with a black tar produced. After the reactants were mixed and stirred a t 0-10' for 2 hr under Nz, the temperature was raised to and maintained at 24-26' for another 2 hr. As in the previous experiment, the absence of the azide band a t 4.61 in the infrared spectrum of the reaction mixture indicated a high conversion. Nmr analysis of both mixtures prior to attempted distillation was that found in Table I for 9. Tlc of the mixture before distillation indicated several very minor impurities, and thus an elemental analysis of 9 was precluded. Reaction of lb with 2b.-A solution of lb (16.3 g, 0.1 mol) and freshly distilled 2b (7.0 g, 0.1 mol) [obtained from Farchan Research Laboratories, bp 45-50' (749 mm),l* nmr (neat with trace TMS) 6 1.34 (t, J = 7 Hz), 1.47 (s), and 4.06 (9, J = 7 Hz)] in benzene (20 ml) was stirred and boiled for 90 hr under Nz. The dark mixture was cooled to room temperature and then distilled Unreacted Ib (9.0 g, 55%) and triethyl phosphate (6.0 g, 33%) were obtained and compared with authentic samples. Glpc (12) Azides l a and lb are described e l ~ e w h e r e . ~ - ~ (13) E. R. H. Jones, G. Eglinton. M. D. Whiting, and B. L. Shaw ["Organic Syntheses," Coll. Vol. IV, N. Rabjohn, Ed., John Wiley & Sons, Inc., New York, N. Y., 1983, p 4041 report a boiling point of 40-51O (749)mm

J . Org. Chem., Vo1. 35,No. 6, 1070 2029

NOTES analysis of the remainder of the product on a 5 ft X 0.125 in. column of 10% Carbowax 20M on 80-100 mesh (DMCS), A-W revealed small amounts (