Intramolecular Nucleophilic Acyl Substitution Reactions Mediated by XTi(O-i-Pr)₃ (X = Cl, O-i-Pr)/2i-PrMgBr Reagent. Efficient Synthesis of Functionalized Organotitanium Compounds from Unsaturated Compounds

Abstract

Treatment of acetylenic or olefinic carbonates and esters with a low-valent titanium reagent diisopropoxy(η2-propene)titanium (1), readily generated by the reaction of Ti(O-i-Pr)4 or ClTi(O-i-Pr)3 with 2i-PrMgX, resulted in an intramolecular nucleophilic acyl substitution (INAS) reaction to afford organotitanium compounds having a carbonyl functional group, in good to excellent yields. Thus, the treatment of alkyl alkynyl carbonates 2 or alkyl alkenyl carbonates 4 with 1 gave organotitanium compounds having a lactone and/or ester group. Similarly, alkyl alkynoates 10 or alkynyl esters 14 of carboxylic acids reacted with 1 to give organotitanium compounds having a cyclic or acyclic ketone group, respectively. Thus, the reaction provides, after hydrolysis, five- or six-membered α-alkylidene lactones and/or α,β-unsaturated esters from 2, γ-butyrolactone derivatives from 4, five- or six-membered α-alkylidene cyclic ketones from 10, and acyclic α,β-unsaturated ketones 15 from 14. In all cases, the yields are excellent and the generation of the organotitanium compounds was confirmed by deuterolysis. The organotitaniums 6 and 11c reacted smoothly with iodine to afford 2-(iodomethyl)-4-butanolide (9) and α-[iodo(trimethylsilyl)methylidene]cyclopentanone, respectively. The organotitanium compounds obtained here also reacted with aldehydes to give the corresponding adducts, thus opening up a new access to substituted α,β-butenolides from 2, to γ-butyrolactones from 4, and to the corresponding tetrasubstituted furan from 10 and 14.

Synthesis and Reactivity of Functionalized Alkynyl Titanium Derivatives

“…In conclusion, the in situ formation of Ti(II) 16 and subsequent reaction with halogeno alkynes offer a new route for the preparation of functionalized alkynyl titanium derivatives. These can further react chemoselectively with func-…”

A New, Mild, General and Efficient Route to Aryl Ethyl Carbonates in Solvent‐Free Conditions Promoted by Magnesium Perchlorate

“…Ethyl octyl carbonate ( 6a ),33 benzyl ethyl carbonate ( 6b ),34 ( E )‐ethyl hex‐2‐enyl carbonate ( 6g ),35 ethyl octan‐2‐yl carbonate ( 6h ),36 ethyl ( R )‐menthyl carbonate ( 6i )27 and ( S )‐ethyl 2‐(ethoxycarbonyloxy) propanoate ( 6j )37 are completely characterized known compounds. ( E )‐ethyl hex‐3‐enyl carbonate ( 6e )38 and ( Z )‐ethyl hex‐3‐enyl carbonate ( 6f )31 are known compounds.…”

Synthesis of 3‐Bromoindenes from 4‐Alkynyl Alcohols/Sulfonamides and Aldehydes via Prins Cyclization, Ring‐Opening and Friedel‐Crafts Reactions

“…9, 138.5, 136.8, 136.2, 129.2, 128.7, 128.7, 127.5, 120.9, 75.9, 61.3, 29.2, 27.7, 21.3 (naphthalen-1-yl) 6, 136.7, 133.9, 130.5, 129.2, 128.7, 128.5, 127.5, 127.4, 127.2, 126.6, 125.4, 125.2, 117.7, 76.2, 61.3, 28.8, 27.9; HRMS (ESI) m/z calcd for [M + H] + (C 22 H 20 BrO) 379.0692, found 379.0677. [30] To a solution of substrates alkynyl alcohol 1 a (40.0 mg, 0.25 mmol), benzaldehyde 2 a (26.5 mg, 0.25 mmol) in benzene (1.0 mL) was added BF 3 · OEt 2 (106.5 mg, 0.75 mmol) at 0°C under a nitrogen atmosphere. After the addition, the reaction mixture was stirred at rt for 1 h, quenched with sat.…”