Trans-Selective Olefination of Carbonyl Compounds by Low-Valent Titanium-Mediated Dehydroxybenzotriazolylation

Abstract

Lithiation with n-butyllithium of a variety of benzotriazole derivatives 1a − f and 5a − d, all containing a proton α to the benzotriazolyl moiety, gave anions which underwent addition to aliphatic, aromatic, and α,β-unsaturated aldehydes and cyclic and acyclic ketones. The resultant N-(β-hydroxyalkyl)benzotriazole derivatives 3a − m, 6a − g, 9a − d, and 10a were dehydroxybenzotriazolylated when treated with low-valent titanium to give alkenes 4a − m, dienes 7a − j, and triene 11a, with selectivity for the trans isomers without separation of diastereoisomeric intermediates. This method offers an alternative to the three most frequently used methods for the formation of alkenes from carbonyl compoundsthe Wittig, Peterson, and Julia reactionsespecially in the formation of tri- and tetrasubstituted alkenes.

The preparation of N-acylbenzotriazoles from aldehydes

“…N-Benzylbenzotriazoles are useful synthetically in many ways. Thus, lithiation with butyl lithium can be followed by the addition to aliphatic, aromatic, and α,β-unsaturated aldehydes; 35 cyclic and acyclic ketones; 35,36 carboxylic esters; 37 enamines 38,39 and imides 40 and leading to the formation of trans-alkenes, dienes , trienes and alkynes. 2-(Benzotriazol-1-yl)enamines (obtained from lithiated 1-(arylmethyl)benzotriazoles and nitriles) undergo rearrangement to give 2,2-diarylquinazolines.…”

1,2,3-Triazoles

“…Further lithiation followed by treatment with ketones provides alcohols 385 ( Scheme 62 ). Upon heating at 60 °C with low valent titanium <1998JOC6704> , alcohols 385 are converted into interesting cyclopropylidene derivatives 386 . 1-(3-Chloro-2-methylpropyl)benzotriazole gives analogous products with a methyl group on the cyclopropane ring <1998JOC6710> .…”

“…Thus, reaction of anions 400 with esters of carboxylic acids leads to α-(benzotriazole-1-yl) ketones 401 , which can be easily reduced to carbinols 402 <1998JOC3438> . In another approach, adducts 402 are produced directly by addition of anions 400 to carbonyl groups of aldehydes or ketones 1997JOC238 , 1998JOC6704 . Low valent titanium, generated by reduction of TiCl 3 with lithium or Zn–Cu couple metals, converts carbinols 402 into olefins 403 ( Scheme 65 ).…”

Efficient and selective olefination of aldehydes with ethyl diazoacetate catalyzed by high-valent tin(IV) porphyrins

“…Generally, the used methods were included the Wittig reaction and its modified reactions, the Peterson reaction, and the Julia reaction [3]. In the past two decades a variety of organometallic compounds have been used for this reaction and some of them was done successfully [4,5]. One of the other procedures for olefin formation is the reaction of carbonyl compounds with diazo compounds in the presence of a reducing agent such as triphenylphosphine and trialkylstibines [6].…”